---There is somebody knocking at the door. Who________ it be?---I’m not sure. It ________ be a postman.
—Do you like our English teacher? —Yes. I think his class is very ________.
This is your pencil. ________ is over there, on the desk.
Doing morning exercises is good ________ our health.
He is going to study hard at math. He wants to be ________ engineer.
--There are forty-eight students in our class. --___________.