问题补充：
--- Tom wants to know.
--- I don know, either. He said he would phone me as soon as he came back.
A. when Dad comes back
B. when did Dad come back
C. when Dad will come back
D. when does Dad come back
答案：
A. when Dad comes back
B. when did Dad come back
(答案→)C. when Dad will come back
D. when does Dad come back
解析：英语宾语从句中一般为陈述语序。根据下文，我也不知道。他说他一回来就给我打电话。可知上文宾语从句中描述的是将来某时发生的动作，故用一般将来时态，选C。
