A lion ____ only attack a human being when it is hungry .
| A．should | B．can | C．will | D．shall |
I got to the lecture hall very early, ______ to get a good rest.
| A．hoping | B．hoped | C．to hope | D．hope |
It hasn’t been announced ______ the plane is to take off.
| A．where | B．when | C．how | D．why |
Students ______ to do some voluntary work every year.
| A．were encouraged | B．are encouraged |
| C．encourage | D．encouraged |
You can smoke here ______ you leave a window open to let the smoke out.
| A．even though | B．so that | C．as long as | D．in case |
It is usually cheaper to have the goods ______ by sea than by air.
| A．sent | B．to send | C．sending | D．being sent |