The sentence that contains the grammatical error is shown below.

Which one of these cookies over there in the bakery case looks most delicious to you?

The error occurs in the sentence's use of the word "these." Later in the sentence, the phrase "over there" is used; this tells us that the cookies are located at some relatively distant position from the speaker and the addressee. Because of this distance, we need to use the demonstrative pronoun "those," which is used for relatively distant people and things, as opposed to "these," which is used for people and things located relatively close by.

The corrected sentence would read,

Which one of those cookies over there in the bakery case looks most delicious to you?

The answer choice that contains the a grammatical error is "Robins are one of the first bird to show up at the beginning of spring." The phrase "one of the first bird" does not make grammatical sense. Here, "one" does not need to agree with "bird." "Bird" needs to be changed to "birds." This is because the sentence is specifying that robins are one out of a group of birds (all birds that show up in spring). Thus, to convey that the speaker is specifying robins as one bird out of a group of birds, the singular "bird" needs to be changed to the plural "birds." The corrected sentence would read, "Robins are one of the first birds to show up at the beginning of spring."

Conjunctions are like grammatical hinges between two ideas. To choose the correct conjunction, we need to analyze how the meanings of the two parts of the sentence connect. In the first part of the sentence, we're told that Francine is forgetful and has something she needs to remember. How might this connect to the idea of writing a grocery list? The first part of the sentence is a cause or impetus for Francine to write a grocery list. So, we need to pick out a conjunction that conveys cause and effect.

The two parts of the sentence do not oppose one another or conflict, so "but," "however," or "nevertheless" cannot be correct. The correct answer is "therefore." This is the only conjunction listed in the answer choices that conveys the cause-and-effect that we logically need for this sentence.

The most logical conjunction for this sentence is "so." The first part of the sentence explains the motivation behind the action that takes place in the second part of the sentence. Conjunctions like "so" and "therefore" convey cause-and-effect relationships like the one in the sentence, so either could work well in the blank. Only "so" is listed amongst the answer choices, so it is the correct answer. "And" is used to connect two sentences when they are not being contrasted or a cause-and-effect relationship between the two parts of the sentence is not at work. "Despite the fact that" is similar to "but" in that one of the parts of the sentence must be working against the other part: "Despite A, B happened." The best answer in this case is "so."