We students should treasure the short senior school’s study life of three years. Once ________, the opportunity can’t get back.

can’t spend _____ money on the car which is _____ expensive for me.

When he knocked at the door, my mother was busy ____ supper

There are ________ floors in the mall and on the _______ floor there are many clothes shops.

d me that he had two girl-friends,and neither of _______ knew anything about the other.