He seemed as if he his homework when his mother came in.A. didB. is to be doingC. were do

问题补充：

He seemed as if he his homework when his mother came in.

A. did

B. is to be doing

C. were doing

D. be doing

答案：

A. did

B. is to be doing

(答案→)C. were doing

D. be doing

解析：这是以as if引导的条件状语从句,一般要用虚拟语气.这是与现在事实相反.所以选C