Once harm ______ to the environment, it takes years to have the system recovered.
| A．does | B．is done | C．will be done | D．be done |
—I’m afraid I must be off now.
—_________.
| A．No problem | B．Never mind |
| C．Step slowly | D．See you |
、Martha Berry was named one of _____ women in the United States.
| A．the twelve most important | B．twelve the most important |
| C．the most important twelve | D．the most twelve important |
—What made ber so sad? —______a good chance to go abroad.
| A．Miss | B．Missed | C．Missing | D．Being missed |
—What made ber so sad? —______a good chance to go abroad.
| A．Miss | B．Missed | C．Missing | D．Being missed |
A professor of biology gave a talk to more than 1000 students on elephants living conditions and the dangers _______ them.
| A．face | B．facing | C．faced | D．are facing |