31. _____ our earth, otherwise it will be no longer fit for us to live on.
| A．Protected | B．To protect | C．Protecting | D．Protect |
— Turn off the TV, Jack. ____ your homework now?— Mum, just ten more minutes, please.
| A．Should you be doing | B．Shouldn’t you be doing |
C．Couldn’t you be doing | D．Will you be doing |
The thief ________ in from the kitchen window as the door was closed.
| A．may climb | B．must have climbed |
C．could have climbed | D．should have climbed |
John, look at the time. ______ you play the piano at such a late hour ?
| A．Must | B．Can | C．May | D．Need |
It is hard for me to imagine what I would be doing today if I _______ in love at the age of seven, with the Melinda Cox Library in my hometown.
| A．wouldn’t have fallen | B．had not fallen | C．should fall | D．were to fall |
— Are you still going to Shanghai for the Spring Festival?
— Yes, but I really _____ because I have a lot of things to deal with.
| A．can’t | B．mustn’t | C．won’t | D．shouldn’t |