Question

-Will Mr Black be here soon?

-I’m not sure, let’s go and see ________．

1. A.
   when will the train arrive
2. B.
   when the train arrives
3. C.
   when the train arrived
4. D.
   the train when will arrive

Answer 1

B
时间状语从句中从句为陈述语序，所以要用when the train arrives．