__ occurred to me that the murder happened _ a rainy day. [ ] A. What; in B. What; on C. It; in

____ occurred to me that the murder happened ___ a rainy day. [ ] A. What; in B. What; on C. It; in D. It; on

正确答案是 D. It; on。

句子意思：我突然想到，那起谋杀案发生在一个雨天。

It occurred to me that... 是固定句型，表示“我突然想到……”，其中用 it 作形式主语。

具体的某一天（或特定某一天的早上、下午、晚上）用介词 on，如 on a rainy day。

所以 It ... on 为正确搭配。