我忘记我们上次什么时候见到他了。

___I ___forget when we last saw him.

青年是未来，我忘了谁说的，但这绝对是正确的。

The youth is the future, ___I ___forget who said that, but it's absolutely true.

我忘了我们协议的具体细节。

___I ___forget the exact details of our agreement.