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.
While most early robot designers equipped their robots with "legs," more recent robot designers have opted for movable treads, which make continual contact with the ground over a wide area in contrast with specific spots on the ground.（）
A. in contrast with
B. rather than at
C. as opposed to at
D. instead of
E. as against
参考答案：B
解析：
The proper answer should contrast the effects of treads with the effects of robotic legs. A and D could be read to contrast specific spots on the ground with the action of making contact over a wide area. C and E are both unidiomatic. B is idiomatic and makes clear that the place at which the robot makes contact with the ground is the thing being contrasted.