March is a Civility month(文明礼貌月) in China. More and more young people are trying to do all they can ________ the elderly.
They have to set out for the last train at once, ________?
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.