21．The moment we heard the news of the earthquake, we began to ________ the work to rescue those who were trapped in the building.
| A．set off | B．set down | C．set aside | D．set about |
Jack always runs faster than Peter, but this time he ______him.
| A．went over | B．fell behind | C．put off | D．dropped off |
The Internet ______it easy to get much new information in a short time.
| A．finds | B．makes | C．feels | D．takes |
We __________out by that time that he_________ a thief for a longtime.
| A．had found, had been | B．had found, was |
| C．found, had been | D．found, was |
It so happened that they________ the novel before.
| A．had read | B．would read | C．were reading | D．Read |
She________ for nearly two hours.
| A．kept talking | B．kept to talk | C．has kept talking | D．kept to talking |