[单项选择]They （　） us since five o'clock this morning until now.
A. are helping
B. help
C. have helped
D. have been helping

[单项选择]They ______ us since five o'clock this morning until now.


A. are helping
B. help
C. have helped
D. have been helping

[单项选择]I arrive at nine o'clock, teach until twelve thirty and then have a meal; that is my morning ______.
A. habit
B. custom
C. practice
D. routine

[单项选择]Since the airport is closed this morning, it must ______ last night.


A. snow
B. have snowed
C. have been snowed
D. have being snowed

[单项选择]Since this road is wet and slippery this morning, it_________ last night.
A. must rain
B. was raining
C. must have rained
D. may rain

[单项选择]Yesterday we ______ school until seven o' clock.

[单项选择]Since the road is wet this morning, （）last night.
A. it must rain
B. it must be mining
C. it must have rained
D. it must have been rain

[单项选择]He ______ get up at five o'clock in the morning.
A. used to
B. is used m
C. has been used to
D. has used to

[单项选择]It took us five hours to get down from the mountain. After having a rest we to the nearest village.


A. proceeded
B. advanced
C. progressed
D. plunged

[单项选择]Since the road is wet this morning, ______last night.
A. it must rain
B. it must be mining
C. it must have rained
D. it must have been rain

[单项选择]Since the road is wet this morning, ______ last night.
A. it must rain
B. it must be raining
C. it must have rained
D. it must have been rain

[单项选择]She told us that five years before, she had been just one of the high school students, but it seemed that overnight she turned into a singer（）
A. 她告诉我们，五年前她不过是一个普通的高中生，然而似乎是在一夜之间她便成了歌星。
B. 五年前她跟我们说，她曾是那些高中生中的一员，但她在黑夜中摸爬滚打才如愿当上了歌星。
C. 她坦白说她是在五年前从一名高中生变成歌星。
D. 她对我们说，她只读了五年书，后来好像时来运转，她突然成了歌星。

[单项选择]Although ______ named until 1812, the metal was used as early as 5100 B.C..
A. it was
B. was not
C. was
D. it was not

[单项选择]Not until Dec. 2003 ______ caught by the US soldiers, and it was a great victory for the USA.


A. was Saddam Hussein
B. Saddam Hussein was
C. had Saddam Hussein been
D. Saddam Hussein had been

[单项选择]American researchers found that the language clock could help ______.
A. count the exact time by years
B. decide when the language came into being
C. make sure when the Aleuts left the mainland
D. determine how the time changed

[单项选择]A Special Clock Every living thing has what scientists call a biological clock that controls behavior. The biological clock________(51) plants when to form flowers and when the flowers should open. It tells insects when to __________(52) the protective cocoon (防护卵袋) and fly away, and it tells animals and human beings when to eat, sleep and wake. Events outside the plant and animal__________(53) the actions of some biological clocks . Scientists recently found, for example, that a tiny animal changes the color of its fur because of the __________(54) of hours of daylight. In the short_________(55) of winter, its fur becomes white. The fur becomes gray brown in _________(56) in the longer hours of daylight in summer. Inner signals control other _________(57) clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration_________(58) twice each year. Birds _________(59) from flying become restless when it is time for the
A. lie
B. sleep
C. stand
D. walk