Three trees can do the job of 15air-conditioners _________ almost all day.
| A．run | B．are running | C．ran | D．running |
The teaching building has five floors. My classroom is ______________ the third floor.
| A．on | B．in | C．at | D．to |
—Open the window please, Mike.
—____________? I didn’t hear what you said.
| A．What | B．Pardon | C．Really | D．All right |
----Do you mind if I sit here? ----________. It’s for Mr Brown.
| A．Not at all. | B．Never mind. | C．Better not. | D．Of course |
Never stand up ________ you are asked to.
| A．if | B．since | C．unless | D．when |
____ Lily ______ Lucy may go with you because one of them must stay at home.
| A．Not only ... but also | B．Both ... or |
| C．Both ... and | D．Either ... or |