He didn't know what was happening outside,为什么happening是进行时?

He didn't know what was happening outside,为什么happening是进行时? He didn't know what was happening outside为什么用进行时 he didn't know what was happening outside 为什么用的是was happenin he didn not know what was happening outside I didn t know what was happening outside这句话中为什么happen加ing? it appeared that he didn't know what was happening=he()()to what is happening outside(用she didn't know 作主句) 再问一个 I didn·t know what was happening.同义句 I didn·t know what what was happening?happening词性 英语同义句替换 2题1.He didn't notice what was happening in front of ''What is happening ouside?'' (用she didn't know作主语） She didn " what is happening?" she asked.为什么是is happening.