He did not know what was______(happen) outside.______上填什么

He did not know what _______. he didn not know what was happening outside What did he play?He ______ ______.怎么填 He did not know what he could do.同意句 He looks unhappy today.What ____(happen)to him? 请问横线上填happen He did not know选择 He did not know what he could expect when he volunteered for he did not know what he should do at that time.改为简单句.he give He did not know how to fight ,but he knocked the boxer 【 】填介 填副词或介词He did not know how to fight,but he knocked the boxer ---We never know what ______(happen)in the future.,） I didn t know what was happening outside这句话中为什么happen加ing?