For any strengthen or weaken question, your job is to find the gap in the logic and either exploit it (in the case of a weaken question) or shore it up (in the case of a strengthen question). Here you are told that some people in the medical community encourage patients to take large doses of vitamin supplements to treat ulcerative colitis. The doctor making this argument claims that the health benefits are no better than the health benefits of getting vitamins through food, so patients with ulcerative colitis should spend their money on food instead of supplements.

The gap here is that ulcerative colitis patients need to eat the food in order to get the vitamins. What if they can’t as a side effect of their disease or can’t afford to buy the foods necessary? Anything that would prevent a patient with ulcerative colitis from getting the nutrients they need from food would exploit this fact.

Choice "Vitamins from supplements are less healthy because they often lack the micronutrients found in food that aid absorption." actually strengthens the doctors argument rather than weakening it. If the supplements were missing important micrnutrients that food has, that would lend support to the idea that it’s better to just get your vitamins through food.

Choice "Vitamins do not necessarily cause harm when ingested following the instructions on the label." neither strengthens nor weakens the argument given. Even if vitamin supplements aren’t harmful, that doesn’t support whether they are better or worse than vitamins ingested through food.

Choice "Many people with ulcerative colitis cannot easily digest vitamin-rich foods due to damage to their digestive system and find it easier to get vitamins from supplements." is correct. If people with ulcerative colitis can’t digest vitamin-rich foods, then they can’t get the same benefit from the food as other people do. Therefore, the doctor’s argument breaks down - if vitamin rich foods and vitamin supplements have the same efficacy but a patient can take vitamins but not foods, then the supplements are more effective in that situation.

Choice "The doctor evaluated the efficacy of different vitamins as part of a government-sponsored panel." simply establishes the doctor as an expert on vitamin research, which does not weaken his argument.

Choice "Individuals with severe ulcerative colitis are often encouraged to consume fruit and vegetable juices alongside their supplements." simply gives additional information about ulcerative colitis treatment unrelated to the debate between eating food and taking vitamin supplements.

The correct answer is "Many people with ulcerative colitis cannot easily digest vitamin-rich foods due to damage to their digestive system and find it easier to get vitamins from supplements.".

In this Weaken question, the accountant argues that "we cannot afford to hire a new salesperson," and then lists as premises the various costs that would add up to a 10% cost increase for the company. What is the gap in logic? Costs are only one part of the profit equation: there's also revenue. And the argument doesn't talk at all about the revenue that this new salesperson could bring in. You should seize on that gap and scan the argument for reasons that revenues would increase more than the costs would.

Choice "Because of the demand for the company’s products, a new salesperson is likely to account for several times as much revenue as the cost of employing her." offers exactly that: if a new salesperson would bring in much more than it costs to employ her, the conclusion crumbles. "Because of the demand for the company’s products, a new salesperson is likely to account for several times as much revenue as the cost of employing her." is correct.

Among the other choices:

"The cost of a computer is a one-time cost and would therefore not affect the company’s recurring monthly expenses." and "Many sales appointments can be conducted via free video conferencing software, thereby reducing the expenses related to mileage reimbursement." each only address one of the many costs of employing the new salesperson, so you're still stuck with the negative premise that monthly costs will be up by 10%. Remember: you cannot argue with the premises, only with the validity of the conclusion.

"The company’s closest competitor employs nearly twice as many salespeople." misses the scope of the argument, which is only about whether the company can afford this new salesperson. Whether or not other companies can afford more employees doesn't factor in to this particular analysis of one company's financial situation.

And "The company will not be able to reduce its existing expenses by enough to counterbalance the costs of a new salesperson." actually strengthens the argument, if anything, demonstrating that the 10% incremental cost is unlikely to be mitigated by other savings.

Since the M.C.A. needs to appear to offer more "healthy" information in its cooking classes, the new programs should address this concern. Since we know that the courses offer classes on fish, grains, and organic vegetables, the correct answer will link these ingredients with health -- as does answer choice "Many advocates of healthy dining stress the importance of including fish, grains, and organically produced vegetables in one's diet.", the correct answer. Answer choice "Cooking fish, grains, and vegetables relies on the same culinary fundamentals as does the preparation of other ingredients." suggests that these classes may be effective for teaching other concepts, but does not speak to the requirement that they appear "healthy." Answer choice "In the food and beverage industry, many employers no longer have time to train apprentices and therefore demand basic culinary skills from their new hires." is irrelevant but does make the M.C.A.'s struggles even more surprising. Answer choice "Local producers in the area near the Metropolitan Cooking Academy are excellent sources of exotic fish and organic vegetables." enables the plan much as "Cooking fish, grains, and vegetables relies on the same culinary fundamentals as does the preparation of other ingredients." does but does not suggest it will succeed in attracting students. Answer choice "Many other cooking schools have found a decline in the level of interest in their programs." offers no helpful information.

In this prompt, the conclusion can be tricky to properly identify because it has two parts to it: “save the money they would spend on radar detectors” and “simply pay the tickets.” The conclusion is essentially saying “radar detectors don’t help drivers avoid tickets,” based on the statistic that radar detector owners get 10% more tickets than those who don’t. But answer choice "Only the drivers most likely to receive speeding tickets purchase and use radar detectors." suggests something else: what if those drivers were actually “supposed to” get twice or three times as many tickets? 10% more would then be a decrease from what you would expect. If only the drivers who are the most likely to get tickets use radar detectors, then it stands to reason that radar detectors do work, even if not all the time. Answer choice "Only the drivers most likely to receive speeding tickets purchase and use radar detectors." is correct.

In this argument, it is concluded that predation by coyotes was the cause of the rabbit decline in Nova Scotia between 2000 and 2010. However, the evidence for this conclusion is quite weak. While disease and undernourishment are eliminated as causes of the decline, it is entirely possible that the decline was caused by a different predator. While deer, the preferred prey for coyotes, did decline in this period, this does not prove that coyotes were responsible for the rabbit decline. Therefore, the correct answer should be something that gives additional evidence supporting coyote predation as the cause of the decline. For "Despite a substantial decline in the deer population between 2000 and 2010, there were still enough deer to support the coyote population in the region.", if this were true, then it would suggest that coyotes were NOT responsible for the rabbit decline as they would still be able to feed off the deer, their preferred prey. For "It is difficult for most wildlife biologists to properly assess whether the decline of an animal population is caused by disease or undernourishment.", this answer choice addresses the possibility that wildlife biologists might have missed some cause relating to disease or malnourishment. However, if this is true and the decline was indeed caused by one of these things, that would weaken not strengthen the conclusion.

For "Between 2000 and 2010, the rabbit population on several islands off the coast that are inaccessible to coyotes did not decline.", this gives additional evidence supporting the conclusion. If there was a place that coyotes were not present over that period and in that place the rabbit population did not decline, this helps build the case that indeed coyotes were the cause. Remember: the given argument provides no evidence that the cause was coyote predation; the only evidence is "it wasn't one of these two things that aren't coyote predation." So any evidence that ties coyote presence closer to rabbit decline is helpful. For "Coyotes are known to eat mice and other vermin, ground birds, insects, and even fish.", whatever else coyotes might eat is not relevant, as you don’t know what happened to those populations and how that would affect coyote predation of rabbits. For "Since 2010, the rabbit population has recovered well while the deer population has declined even further." whatever happened since 2010 is not important, as this argument is only concerned with explaining a decline during the particular period from 2000 to 2010. The correct answer is "Between 2000 and 2010, the rabbit population on several islands off the coast that are inaccessible to coyotes did not decline.".

Whenever you are asked for an answer that "most logically completes" an argument, you can determine what type of question you're dealing with by looking immediately before the blank that the answer will fill in. Here that blank is preceded by "since," so you're looking for a reason, and before that it's "these processes do not prevent harm from some drug enantiomers." So you're looking to provide a reason that these processes don't prevent harm - you're looking to strengthen that idea.

In any strengthen/weaken problem it is extremely helpful to notice the gap in logic between the premises and conclusion, and here the "extra" information just before the conclusion gives you great insight into that. Notice the modifier "during the drug creation process" - that gives a good deal of specificity as to where the prevention of harm takes place. It limits the prevention of enantiomers to that narrow scope "during the drug creation process," leaving enantiomers to emerge during any other time period (during transport of the drugs, the drugs' interaction with their containers, when taken in combination with other drugs or foods, etc.). If you notice that, you can scan the answer choices looking for some other timeframe when these enantiomers emerge.

Choice "the metabolism of some drugs within the body can create harmful enantiomers regardless of whether the drug itself contains those enantiomers." gives you exactly such a situation where this could happen. If the metabolism of the drugs leads to the creation of the harmful enantiomers, then there is no way that changes in the production process can mitigate the effects of harmful enantiomers. Choice "the metabolism of some drugs within the body can create harmful enantiomers regardless of whether the drug itself contains those enantiomers." exploits that gap in logic and is correct.

Among the other answers, choice "not all drug enantiomers are harmful and some can even be helpful in fighting certain diseases." can be eliminated because the argument is about exposure to harmful enantiomers, not whether all enantiomers are necessarily bad. Choice "many enantiomers only cause minor side effects rather than major health problems when ingested." can be eliminated because the argument is about limiting consumer exposure to all harmful enantiomers regardless of severity. Choice "the creation of harmful enantiomers are not the only side effect that drug manufacturers should seek to reduce." can be eliminated because the argument is only about enantiomers, not other side effects, and choice "enantiomers are difficult to detect and cannot be pinpointed as the cause of some health problems." can be eliminated because it does not deal with whether it is possible to limit consumer exposure to harmful enantiomers.

As you assess the argument, you should notice that there is very little direct evidence given for the conclusion that tusks without imperfections are almost certainly counterfeits. The premises only state that there is demand for tusks and that the counterfeiting of tusks is now an industry, but the conclusion is specific to one particular feature of tusks - if they're free from imperfection, they're counterfeit - without any evidence given for that. So your goal in the answer choices should be to find either a link between imperfections and authenticity or a link between perfect tusks and counterfeiting.

Choice C provides that first link: if real elephant tusks are often imperfect because of the way that elephants use their tusks, then it stands to reason that perfect tusks likely aren't authentic. Choice "Elephants regularly use their tusks to scrape bark from trees, a process that leads to the frequent chipping and breaking of tusks." is correct.

Among the incorrect answer choices, choice "Counterfeit ivory is often damaged during shipping due to the fragile material necessary to make the product cost-effective." actually weakens the argument by giving a reason why counterfeit tusks would have imperfections. And choices "Many ivory purchasers are aware of the counterfeit market and are as happy with fake ivory as they would be with real ivory.", "Some governments in developing economies have encouraged the counterfeit ivory market as a way to satisfy demand without harming animals to increase the supply.", and "The process of counterfeiting ivory has become so sophisticated that it is difficult for most people to tell the difference between authentic and counterfeit tusks." miss the point of the conclusion entirely - none of them deals with the link between perfect tusks and counterfeit tusks.

Recognize, also, an important lesson here: extra words (modifiers, adjectives, etc.) matter in conclusions! The most popular incorrect answer choice, "The process of counterfeiting ivory has become so sophisticated that it is difficult for most people to tell the difference between authentic and counterfeit tusks.", gives a reason that buyers should be careful in general. But the conclusion is that buyers should beware specifically of those tusks that have no imperfections. That modifying phrase "that have no imperfections" is crucial to your understanding of the argument.

With Strengthen/Weaken problems, it is important to read adjectives, modifiers, and anything else "additional" that specifies the conclusion, as that is often where the gap in logic lies. Here the conclusion is "clearly, the students are misinformed in their complaint," which should encourage you to look at the specificity of that complaint. Their complaint is not about "class sizes" in general, but more specifically "the size of classes taught by the most popular professors."

This is critical, as it sets up the gap: the statistic given is about the general student-to-teacher ratio, not the ratio for those specific classes taught by the most popular professor. So as you approach the answer choices, you're looking to exploit that gap: how could the overall ratio have become lower, while the ratio for the classes in question have gotten higher.

Choice "Many of the most popular tenured professors commonly teach courses that have ten times the number of students enrolled in an average course." exploits that gap perfectly: if the classes of the most popular professors have 10 times the typical number of students, then the general ratio doesn't apply to the specific complaint. Therefore, choice "Many of the most popular tenured professors commonly teach courses that have ten times the number of students enrolled in an average course."is correct.

Among the other answer choices, choice "Most of the faculty members at the university are part-time instructors or teaching assistants and not full-time, tenure-track professors." is a good distracter choice. It would seem that if most of the faculty members are not full-time professors that the professors would have larger classes, yet this requires an assumption that choice "Many of the most popular tenured professors commonly teach courses that have ten times the number of students enrolled in an average course." does not. With choice "Most of the faculty members at the university are part-time instructors or teaching assistants and not full-time, tenure-track professors." it is still possible that all courses have even numbers of students and those courses taught by full professors have only 14 students. Choices "Some other universities in the state have lower faculty-to-student ratios." and "The average class size at the university varies from department to department." do not bear directly on the question as to whether the size of the courses of popular professors is increasing. Even if true, Choice "None of the students who complained is willing to pay increased tuition in order to have smaller classes." does not indicate whether the students are misinformed in their claims about class size.

On this Strengthen question, note the potentially paradoxical logic the fire departments use. Their concern is safety (an important clue the testmakers leave in the sentence that outlines the departments' actions), so why would they choose not to extinguish small fires?

Choice "Only some small brush fires expand to become large, catastrophic fires." is inconsistent with the idea of safety. Even "only some" small fires turn into catastrophic fires, failing to extinguish them risks or sacrifices at least some safety. And that is certainly not a reason to actively choose not to extinguish them in the name of safety.

Choice "Most fire departments would be unable to extinguish every small brush fire without having to hire additional staff." also falls victim to the notion of safety. If the fire departments had cited cost as their reason, then "Most fire departments would be unable to extinguish every small brush fire without having to hire additional staff." totally works - hiring more firefighters to fight these small fires would certainly come at a cost. But if their cited concern is safety, the reason that "we would have to hire more people and spend more money" is not consistent with their stated goals/priorities.

Choice "There is no means other than fire for clearing dry brush and debris in wildfire-prone areas." is correct. If letting the small fires burn is the only known way to eliminate the brush that could fuel a larger fire, then choosing to not extinguish the fire works with the idea of safety - that decision is made to help prevent larger fires from having sufficient fuel to be catastrophic.

Choice "The most common causes of small brush fires are carelessly-discarded cigarette butts and poorly-extinguished campfires, each of which is easily preventable through fire education." is incorrect in large part because of its timeline. The departments are choosing not to extinguish fires that are already burning, so relying on education to prevent new fires from starting isn't a valid reason - that solution will do nothing to help the existing fires.

And choice "Small brush fires enrich the soil beneath them, leading to fertile land for agriculture and natural beauty." simply misses the mark of safety - sure, the fires might leave a beautiful, productive landscape but if safety is a cost of that then the fire departments are violating their stated reason for the choice not to extinguish the fire.