Question

-I don't know ________ he will come tomorrow．

-Don't worry．________ he comes, I'll let you know．

1. A.
   whether, If
2. B.
   if, Whether
3. C.
   when, Whether
4. D.
   that, If

Answer 1

A
这里的语境为：“我不知道明天他是否会来．”“别担心，如果他来了，我会告诉你的．”