1.When did you went to the library?-Three hours ago.
2.It has been two hours since he has been here.
3.The girl has been asleep since 9 o'clock.
4.They have known each other for ten years.
1.When did you went to the library?-Three hours ago.
2.It has been two hours since he has been here.
3.The girl has been asleep since 9 o'clock.
4.They have known each other for ten years.