I know Mr. Brown；we ＿＿ to each other at an international conference.
| A．are introduced | B．have been introduced |
| C．were introduced | D．had been introduced |
-What are you worried about?
-Tom didn't respond ______ any of my e-mails. Something must have happened to him.
| A．on |
| B．with |
| C．for |
| D．to |
It is almost ______ that every organization has too many meetings, most of which are poorly prepared.
| A．expected |
| B．certain |
| C．secure |
| D．powerful |
-Can I smoke here?
-Sorry. We don't allow ______ here.
| A．people smoking |
| B．people smoke |
| C．to smoke |
| D．smoking |
Once harm is ______ to the eco-system, all species will ______ , including man himself .
| A．made; be in danger |
| B．done; be dangerous |
| C．caused; be endangered |
| D．done; be in danger |
With no more wood added to the fire, it finally died ______
| A．away |
| B．from |
| C．out |
| D．off |