I like in the early morning when the air is fresh and I can take a walk around the garden.

问题补充：

I like in the early morning when the air is fresh and I can take a walk around the garden.

A. that

B. it

C. which

D. what

答案：

A. that

(答案→)B. it

C. which

D. what

解析：考查it作为形式宾语。代替的是in the early morning.介词短语不可充当宾语，故用it来代替。when引导的是定语从句。