We were told not to touch the equipment in the laboratory unless ________.
| A．allowed to do | B．allowing to do |
| C．allowed to | D．allowing to |
—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 |
He was unhappy when he sold his guitar.After all，he________it for a very long time.
| A．has had | B．had had | C．has | D．had |
—Oh no! We're too late.The train________.
— That's OK.We'll catch the next train to London.
| A．was leaving | B．had left |
| C．has left | D．has been leaving |