_______you return those books to the library immediately, you will have to pay a fine.[ ]

Emergency line operators must always _____ calm and make sure that they get all the information they needto send help.[ ]

I thought she was the very girl that Ishould marry _______ I met her.

TFBOYS’ songs ____ sweet and many of us like listening to them.

Lin Shuhao is now one of ________ basketball players in the NBA.