你定语从句掌握不太好啊,你看啊,the reason做的是gave的宾语吧,he gave the reason for his absence,宾语的先行词不是只有that which 吗,不要一看到reason就想选why.
再给你个用why的,你自己区别一下：I’d like to know the reason why you’re so late.
再给你一个：We aren’t going for the simple reason that we can’t afford it.同位语从句