-They arrived Guangzhou a rainy morningA. in; inB. at; inC. in; onD. at; on

问题补充：

-They arrived Guangzhou a rainy morning．

A. in; in

B. at; in

C. in; on

D. at; on

答案：

A. in; in

B. at; in

(答案→)C. in; on

D. at; on

解析：句意：我们在一个下雨的上午到达广州。arrive in+大地点，arrived at +小地点。时间前有天气的形容词修饰，用介词on,故选C。