The following questions present a sentence, part of which or all of which is underlined. Beneath the sentence you will find five ways of phrasing the underlined part. The first of these repeats the original; the other four are different. If you think the original is best, choose the first answer; otherwise choose one of the others.
These questions test correctness and effectiveness of expression. In choosing your answer, follow the requirements of standard written English; that is, pay attention to grammar, choice of words, and sentence construction. Choose the answer that produces the most effective sentence; this answer should be clear and exact, without awkwardness, ambiguity, redundancy, or grammatical error.
Many doctors direct their patients to name-brand drugs, but smart consumers know that generic drugs cost half as much as buying name-brand drugs.（）
A. generic drugs cost half as much as buying name-brand drugs
B. buying generic drugs costs half as much as name-brand drugs
C. generic drugs cost half as much as name-brand drugs
D. buying generic drugs cost half as much as buying name-brand drugs
E. to buy generic drugs costs half as much as buying name-brand drugs
参考答案：C
解析：
The correct answer should relate the cost of "generic drugs" to the cost of "name-brand drugs," or "buying generic drugs" to "buying name-brand drugs;" in any event, the constructions should match. C and D are the only answers that provide appropriate parallel constructions, but D makes a grammatical error by using a plural verb, "cost," with a singular subject, "buying." C is the correct answer.