The field research will take Jone and Paul about five months; it will be a long time ____we meet them again.
A. after B before C since D when
---I beg your pardon!
---Oh, youto me carefully. (just now)
| A．didn’t | B．haven’t listened | C．don’t listen | D．weren’t listening |
． Knowledge of English is a must in international trade.
| A．the | B．/ | C．A | D．An |
Where on earth have you been? We you back much earlier.
| A．were expecting | B．are expecting | C．had expected | D．expect |
Cloning the sheep ----Dolly is a big in science.
| A．progress | B．run | C．jump | D．rush |
He works in a factory now, but he on a farm for 20 years.
| A．worked | B．has worked | C．had worked | D．had been working |