He seems too tired today and I wonder he got a good sleep last night.A. whenB. thatC. if

问题补充：

He seems too tired today, and I wonder he got a good sleep last night.

A. when

B. that

C. if

D. where

答案：

A. when

B. that

(答案→)C. if

D. where

解析：

他今天看起来很累，我怀疑他昨晚是否睡好了。if引导宾语从句。故选C。