—Catherine, I have cleaned the room for you.
—Thanks. You ______ it. I could manage it myself.
| A．needn't do | B．needn't have done |
| C．mustn't do | D．shouldn't have done |
—I’ m sorry that I have broken your glasses.
— ____________!
| A．Never mind | B．Not at all | C．You’re welcome | D．With pleasure |
______ is often the case, we have worked out the production plan.
| A．Which | B．When | C．What | D．AS |
The flu is believed _____by viruses that like to reproduce in the cells inside the human nose and throat.
| A．causing | B．being caused | C．to be caused | D．to have caused |
—How did you find the talk this morning?
—______.
| A．By asking my students | B．It was easy to find |
| C．Very disappointing | D．Just in time for it |
The flowers _________sweet in the botanic garden attract the visitors to the beauty of nature．
| A．to smell | B．smelling | C．smelt | D．to be smelt |