________ is as much an art as it is ________ science.
| A．Cloning; a | B．Clone; / | C．To clone; the | D．Cloning; the |
Mr. Irvine, who ________ in a high school for forty years, is now living in retirement.
| A．had taught | B．taught | C．has taught | D．had been teaching |
－We could have asked Mr. Zhang for help. He is always ready to help others.
－I ________ that. A long time _______.
| A．have forgot, wastes | B．forgot, wasted |
| C．forgot, was wasted | D．forgot, has been wasted |
Both teams are among the most excellent. We mustn’t miss the ______ game.
| A．strong | B．difficult | C．close | D．crazy |
Mary must keep her mind on her medical studies now, so it would be years ______ she could think about marriage.
| A．before | B．when | C．since | D．until |
His sudden ______ of violent anger put an unpleasant end to the meeting.
| A．break | B．burst | C．attack | D．express |