Official Explanation
(A) This answer choice maintains Parallelism by matching the subject (
Giffen good) with a noun (
product).
(B) This answer choice is
grammatically incorrect. The relative clause that does not necessarily occur in the real world describes the noun that appears immediately before it, namely, theories. Since theories is
plural, the verb that follows it also needs to be
plural. However, does is
singular.What helps us identify this question as a
Relative Clause question as well as identify the mistake is the following
Stop Sign: one of the + plural noun + who/which/thatWhenever you see this
Stop Sign, make sure that the following verb is
plural.
(C) This answer choice is
grammatically incorrect due to a
Parallelism error. Whenever you come across a sentence containing the structure
A is/means B make sure that:
(A) A and
B are
grammatically parallel (i.e., of the same
part of speech).
(B) A and
B are
logically parallel.In this answer choice,
A is a noun (
Giffen good) whereas
B is a
present participle (ing verb rising).
What helps us identify this kind of
Parallelism error and correct it is the following
Stop Sign: A is/means B(D) This answer choice is
illogical. The
subject of the second part of the sentence is the term. A term cannot be an economic theory. We cannot say that a word or term is something or other, but a word or term can refer to/define/describe something or other.
What helps us identify this mistake is the following
Stop Sign:The word/term... (it) is...Whenever we see this
Stop Sign, we know that the topic that the question checks is
pronouns, specifically using refers to/defines/describes after the word/term (and not is).
(E) Same as
(C)Answer: A