---Do you often spend half an houryour homework every day?---Yes I do.A. forB. inC. atD.

问题补充：

---Do you often spend half an houryour homework every day?---Yes, I do.

A. for

B. in

C. at

D. On

答案：

A. for

B. in

C. at

(答案→)D. On

解析：在英文中和spend搭配表示在做某事上花费多长时间用doing的形式，或介词on，故本题选D。