Question

【题目】You should inspect the wheels regularly, and replace them ______ they cause you trouble.
A.while
B.when
C.before
D.until

Answer 1

【答案】C
【解析】句意：你应该在出事之前经常检查车轮并及时更换。A.while”当.....时，然而”；B. when“在.......时候，随着”；C.before 在......之前“；D. until”直到.....才“。故选C。