问题补充：
---Do you know back tomorrow?
- --Sorry, I don’t know. When he back, I’ll tell you.
A. when does he come, comes
B. when he comes, will come
C. when he will come, comes
D. when will he come, will come
答案：
A. when does he come, comes
B. when he comes, will come
(答案→)C. when he will come, comes
D. when will he come, will come
解析：根据时间状语，上句问的是将来发生的事情，故用将来时态。主句为将来时态时，从句用一般现在时态，故选C。
