This is the reason I agree to it.A. thatB. whyC. whatD. A and B

问题补充：

This is the reason I agree to it.

A. that

B. why

C. what

D. A and B

答案：

A. that

B. why

C. what

(答案→)D. A and B

解析：名词reason后多接why（定语从句），可接that（同位语从句），有时for（+代词引出定语从句）。