--- Who broke the window? --- I _____.
| A．had | B．broke | C．was | D．did |
—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 |
—What do you think we can do for our aged parents?
—You ________ do anything except to be with them and be yourself.
| A．don’t have to | B．oughtn’t to | C．mustn’t | D．can’t |
His lack of professional knowledge _______for the failure of the experiment.
| A．accounted | B．explained | C．counted | D．contributed |
Not believing their eyes, the visitors on the spot _______ the flying plane, doing some most difficult and dangerous tricks in the sky.
| A．glared at | B．stared at | C．glanced at | D．caught sight of |