I couldn't remember后从句应用什么时态?

问题描述:

I couldn't remember后从句应用什么时态?
还有,You must give the wallet back to whom it belongs to..此句为何语法正确?whom前面不是应该加被其修饰的名词(the person)吗?

I couldn't remember +过去时
You must give the wallet back to whom it belongs to.这里whom做了to的宾语,引导宾语从句
如果是定语从句的话前面要有the person