let him go；但是我想用when只修饰go，即they let him go when.的疑问句怎么变？（they asked him to leave and do I know when exactly he left?我想表达的是这个意思）

② If you could make him change his mindyou would save him a lot of trouble.这句话能不能看成不是虚拟？（因为如果这句话是间接引语，它的直接引语可能会有两种，一种是'If you can make him change his mindyou will save him a lot of trouble.' 还有种还是它不变）