Brass is an alloy of copper, and steel is an alloy of iron. 

"Dune" is a noun defined as a mound of sediment, such as sand. Because dunes are composed of sand, we need to pick out an answer choice that refers to the substance of which a drift can consist. "Drift" is defined as a pile of snow, leaves, or other material formed by the wind, so "snow" is the correct answer because just as sand forms dunes when it is blown into piles by the wind, snow forms drifts when it is blown into piles by the wind.

A bottle might logically be made of glass, so we need to pick out an answer choice in which the first word is a noun conveying an object, and the second word a noun describing a material of which that object might logically be made. While “box is to cardboard,” “table is to air,” and “wall is to gelatin” each follow the pattern of a word conveying an object followed by a word conveying a material, one would not expect a table to be made of air or a wall to be made of gelatin, so neither “table is to air” nor “wall is to gelatin” can be the correct answer. One might logically expect a box to be made of cardboard, however, just as one might logically expect a bottle to be made of glass, so “box is to cardboard” is the correct answer.

Since boxes can be made of cardboard, we need to pick out an answer choice in which the first word describes a substance of which the second word can be made. Both "clay is to pot" and "metal is to chain" could be correct answers. However, "clay is to pot" is the better answer because a pot, like a box, is a type of container, unlike a chain. So, the correct answer is "clay is to pot."

In a "square" and a "circle" the distance from the center to any point on the outside is always the same as the distance from the center to any other point on the outside. A "circle" might be seen as "a round square." So, which of these could be seen as a "round rectangle?" The correct answer is an "oval." An "oval" is a round, elongated shape. Additionally, a "sphere" is a three-dimensional circle, an example of a "sphere" is a "globe."

A group of "tradesmen" is called a "guild." So, to solve this analogy you need to determine which of these, when taken as a group, is called a "coven." The correct answer is that a "coven" is a group of "witches." 

An "encyclopedia" is a book that contains a collection of "information." So, to solve this analogy you need to determine what an "anthology" is a collection of. The correct answer is that an "anthology" is a collection of "stories."

"Downs" are small, rolling hills made of "grass." So, to solve this analogy you need to determine what it is that "dunes" are made of. The correct answer is that a "dune" is made of "sand." "Dunes" are typically found in the "desert."

A "portfolio" is a collection of "artwork" produced by an individual. So, if a "portfolio" is a collection of "artwork," what is a "troupe" a collection of? The correct answer is that a "troupe" is a group of entertainers, like "artists" or musicians, who travel and perform together. 

"Lumber" is timber that has been chopped into planks. It is made from "wood," so to solve this analogy you need to determine what an "anvil" is made from. Well, an "anvil" is made from "iron," it is a type of "hammer" used to shape metal.