To his credit,Tom never told the enemy exactly what had happened.
问题描述：
To his credit,Tom never told the enemy exactly what had happened.
"happened"前面可以加had吗?不是一般都直接写成what happened.
答
had happened是过去完成时,指过去的过去发生的动作.
Tom never told the enemy exactly what had happened.
told说明是过去式,而不告诉敌人发生过什么就是“过去的过去”,要用had happened
what happened一般用于问句.