—Hey, if you can't enjoy that at a sensible volume, please use the earphone. I'm studying.—Oh, I'm sorry. I_______ _realize it________ you.
He said that he would write to us but so far we ___________ from him.
__________ good exercise.
I don’t know who invented __________ telescope, but I think it is __________ most useful invention.
Rarely _____________________ .
This is the only way we can imagine _______ the overuse of water in the students’ bathrooms.