—We’ll have a hiking trip tomorrow but when shall we meet?—Let’s make it half past seven.

问题补充：

—We’ll have a hiking trip tomorrow, but when shall we meet?

—Let’s make it half past seven.

A. on

B. in

C. to

D. at

答案：

A. on

B. in

C. to

(答案→)D. at

解析：D 钟点前用介词at。“让我们约在7:30吧。”