We must do whatever we can _____ the river _____ any more.
| A．to keep; polluted | B．to prevent; being polluted |
| C．keep; polluted | D．prevent; being polluted |
—It's the office！So you ________ know eating is not allowed here.
—Oh，sorry.
| A．must | B．will | C．may | D．need |
Keep up good state of mind even if you ________ fail plenty of times.
| A．must | B．will | C．can | D．should |
A left－luggage office is a place where bags ________ be left for a short time，especially at a railway station.
| A．should | B．can | C．must | D．will |
Oh，I'm not feeling well in the stomach.I ________ so much fried chicken just now.
| A．shouldn't eat | B．mustn't have eaten |
| C．shouldn't have eaten | D．mustn't eaten |
He hesitated for a moment before kicking the ball，otherwise he ________ a goal.
| A．had scored | B．scored |
| C．would score | D．would have scored |