Question

We never visit a friend's house without calling first.

1. A.
   if we don't call first
2. B.
   when calling first
3. C.
   unless we call first
4. D.
   A and C

Answer 1

D
考查词义理解。without短语在句中做条件状语，表示“如果不……”，由句意“如果事先不打电话，我们从不去朋友的家”。B项恰好与题意相反。