It was not until 3 days later that the boy came back to life and explained to the police w

问题补充：

It was not until 3 days later that the boy came back to life and explained to the police what to him.

A. was happening

B. was to happen

C. had happened

D. has happened

答案：

A. was happening

B. was to happen

(答案→)C. had happened

D. has happened

解析：考查时态。句意为：两个星期后，那个男孩才苏醒过来，向警方解释到底发生了什么事。happen发生在explain之前，是“过去的过去”，用过去完成时。