I was out of town at that time, so I don’t know exactly how it .
A. was happening
B. happened
C. has happened
D. happens
网友回答
A. was happening
(答案→)B. happened
C. has happened
D. happens
解析：考查时态。句意：在那时我在城外。使用我不知道那件事情是如何发生的。根据关键词at that time，这是一个很清楚的过去时的时间状语，可知指在过去某个时间发生的事情，故使用一般过去时，故B正确。