By the time Einstein was 14 years old, he himself advanced mathematics.
| A．has taught |
| B．taught |
| C．had taught |
| D．was teaching |
The next day, the group of villagers had not gone very farthey entered a very narrow passage betweentwo mountains．
| A．when | B．while | C．until | D．after |
Mr Black, who we all admire, is a kind but strict teacher．
| A．the one | B．it | C．one | D．as |
—Does your father smoke?
—,it's 2 years since he．
| A．Yes; smoked | B．No; smoked | C．Yes; smokes | D．No; has smoked |
Do you know theof the saying I just quoted?
| A．resource | B．cause | C．course | D．source |
Liu Xiang's Olympic dreams were shattered（破灭）forsecond time when he unfortunatelycrashed at first barrier in the ll0m hurdles heats in London．
| A．the; the | B．a; a | C．a; the | D．the; a |