问题补充：
I don’t know . When he . I will phone you.
A. when will be some back, comes back
B. when is he coming back, will come back
C. when he comes back, is coming back
D. when he is coming back, comes back
答案：
A. when will be some back, comes back
B. when is he coming back, will come back
C. when he comes back, is coming back
(答案→)D. when he is coming back, comes back
解析：此题重点考查when引导宾语从句和时间状语从句的不同。前者要用陈述句语序，且时态要和主句保持一致；后者常用一般现在时。
