I was out of town at the time, so I don’t know exactly how it .
A. was happening
B. happened
C. happens
D. has happened
网友回答
A. was happening
(答案→)B. happened
C. happens
D. has happened
解析：
考查动词的时态。根据前面的I was out of town…，可知happen这个动作发生在过去，故用一般过去时。本句的意思是：那个时候我不在城里，因此我不能确切地知道它是怎样发生的。