I was out of town at the time ,so I don't know exactly how it ___.A was hapening B.happened

问题描述:

I was out of town at the time ,so I don't know exactly how it ___.A was hapening B.happened
为啥选 B

这个句子可以改写成:When it happened,I was out of town.But I don't know exactly how it did(= happened).在这里,HAPPEN是瞬间动词,不必用进行时.又如,When the accident happened,John was swimming in the poo...