—Look! The man at the gate _______be our headmaster. He is always standing there every morning.—No, it_______ be him. He is holding a meeting in the office now.
Students are warned ________ in the exam, otherwise they will be severely punished.
I am wondering ________ you have read “the Harry Potter series” written by JK Rowing.
It is better for you to walk down the stairs instead of ________ the elevator.
He told us that he was tired and thirsty because he ________ in the desert for days.
My mother ________ as an architect since she graduated from Tongji University.