问题
选择题
--- We'll visit the Summer Palace_______ there is a heavy rain tomorrow.
--- OK ! Boating on the lake must be interesting.
A．unless
B．since
C．until
D．if
答案
答案：A
题目分析：句意：如果明天没有大雨我们就将参观颐和园。A unless如果不B. since自从C. until直到D. if如果。根据句意，故选A。
