---What are you going to do Sunday morning?Nothing much.A. /B. onC. inD. at

问题补充：

---What are you going to do Sunday morning?

--- Nothing much.

A. /

B. on

C. in

D. at

答案：

A. /

(答案→)B. on

C. in

D. at

解析：介词at用于具体时刻；介词on用于具体的一天；介词in用于一段时期。本句是指Sunday morning，是具体的一天，故用on.