Question

Beneath each of the following sentences there are four choices marked A, B, Cand D. Choose the one answer that best completes the sentence.Small sailboats can easily turn over in the water ______ they are not managed carefully.

1. A.
   though
2. B.
   before
3. C.
   until
4. D.
   if

Answer 1

D
思路分析：句意为：小航船如果操作不小心很容易在水里翻了。由此知前后两句是主从条件句。though引导让步状语从句；before和until都引导时间状语从句。
【点评】本题考查状语从句，难度偏适中。