Question

--- 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

Answer 1

A

试题分析：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。