---Do you know when Dr Smithfor dinner this evening?----No but I think he when he is free.

问题补充：

---Do you know when Dr Smithfor dinner this evening?

----No,but I think he when he is free.

A. will come;comes

B. will come;will come

C. comes;comes

D. comes;will come

答案：

A. will come;comes

(答案→)B. will come;will come

C. comes;comes

D. comes;will come

解析：句意：你知道史密斯博士今晚什么时候来吃晚饭吗？——不知道，但是我想如果他有空他会来的。结合语境可知本题上下文都是宾语从句，描述的是将来某时发生的动作，故都用一般将来时态，选B。