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.