My father will be back the morning of May 15. A. inB. atC. onD. since

问题补充：

My father will be back the morning of May 15.

A. in

B. at

C. on

D. since

答案：

A. in

B. at

(答案→)C. on

D. since

解析：此题考查介词的用法，表示具体某天的上午下午或晚上要用介词on。句意：我的父亲将在五月十五日的上午会回来。所以选C。