I really don’t know .A. to swimB. how to swimC. to swim howD. how swim

问题补充：

I really don’t know .

A. to swim

B. how to swim

C. to swim how

D. how swim

答案：

A. to swim

(答案→)B. how to swim

C. to swim how

D. how swim

解析：考查非谓语动词。特殊疑问词+to do相当于一个宾语从句。句意“我确实不知道怎样游泳。”故选B。