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【单选题】
PN结加反向电压,少数载流子难以注入,故不发光。当它处于正向( ) 时(即两端加上正向电压),电流从LED 阳极 流向阴极时,半导体 晶体 就发出从紫外到红外不同颜色的光线,光的强弱与电流有关。
A.
截止状态
B.
工作状态
C.
饱和状态
D.
半导通状态
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举一反三
【单选题】It was reported that an agreement ____ between the two companies and that they would carry out a project together.
A.
reached
B.
had been reached
C.
was reached
D.
has been reached
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【单选题】Why was the passenger jet forced to land at Halifax, Canada?
A.
Some passengers would get off the plane in Canada.
B.
There was something wrong about the plane and it could not fly again.
C.
Because there were criminals on the jet plane.
D.
Because it had been thought that the jet had been hi-jacked.
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【单选题】I am afraid to sleep. I have been afraid to sleep for the last few weeks. I am so tired that, finally, I do sleep, but only for a few minutes. It is not a bad dream that wakes me it is the reality I t...
A.
refused to speak to her
B.
was pleasant and attractive
C.
was selling skirts and ribbons
D.
recognized her immediately
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【单选题】不属于间脑的结构是
A.
是中脑背侧面上丘和下丘的总称
B.
为大脑皮质重要的按觉中枢
C.
其内的中间带外侧核为内测丘系的中转站
D.
以上都不对
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【单选题】--Did you sleep well yesterday? -- Never _____. I fell into a deep sleep the moment I went to the bed.
A.
bad
B.
worse
C.
better
D.
best
查看完整题目与答案
【单选题】I can sleep for 7 hours every day now, but if I take that job, I ____less time for        sleep.
A.
had
B.
haven’t had
C.
will have
D.
wouldn’t have
查看完整题目与答案
【单选题】I like ________ a little longer ________ weekends. [     ]
A.
sleep, on
B.
to sleep, on
C.
sleep, in
D.
to sleep, in
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【单选题】People______ that vertical flight transports would carry millions of passengers as do the airliners of today.
A.
comprehended
B.
anticipated
C.
revealed
D.
asserted
查看完整题目与答案
【单选题】What options would they offer to passengers?
A.
Hot beverages
B.
Steamed buns
C.
Light meals
D.
All of the above
查看完整题目与答案
【单选题】It was reported that an agreement ____ between the two companies and that they would carry out a project together. [     ]
A.
reached
B.
had been reached
C.
was reached
D.
had reached
查看完整题目与答案
相关题目：
【单选题】It was reported that an agreement ____ between the two companies and that they would carry out a project together.
A.
reached
B.
had been reached
C.
was reached
D.
has been reached
查看完整题目与答案
【单选题】Why was the passenger jet forced to land at Halifax, Canada?
A.
Some passengers would get off the plane in Canada.
B.
There was something wrong about the plane and it could not fly again.
C.
Because there were criminals on the jet plane.
D.
Because it had been thought that the jet had been hi-jacked.
查看完整题目与答案
【单选题】I am afraid to sleep. I have been afraid to sleep for the last few weeks. I am so tired that, finally, I do sleep, but only for a few minutes. It is not a bad dream that wakes me it is the reality I t...
A.
refused to speak to her
B.
was pleasant and attractive
C.
was selling skirts and ribbons
D.
recognized her immediately
查看完整题目与答案
【单选题】不属于间脑的结构是
A.
是中脑背侧面上丘和下丘的总称
B.
为大脑皮质重要的按觉中枢
C.
其内的中间带外侧核为内测丘系的中转站
D.
以上都不对
查看完整题目与答案
【单选题】--Did you sleep well yesterday? -- Never _____. I fell into a deep sleep the moment I went to the bed.
A.
bad
B.
worse
C.
better
D.
best
查看完整题目与答案
【单选题】I can sleep for 7 hours every day now, but if I take that job, I ____less time for        sleep.
A.
had
B.
haven’t had
C.
will have
D.
wouldn’t have
查看完整题目与答案
【单选题】I like ________ a little longer ________ weekends. [     ]
A.
sleep, on
B.
to sleep, on
C.
sleep, in
D.
to sleep, in
查看完整题目与答案
【单选题】People______ that vertical flight transports would carry millions of passengers as do the airliners of today.
A.
comprehended
B.
anticipated
C.
revealed
D.
asserted
查看完整题目与答案
【单选题】What options would they offer to passengers?
A.
Hot beverages
B.
Steamed buns
C.
Light meals
D.
All of the above
查看完整题目与答案
【单选题】It was reported that an agreement ____ between the two companies and that they would carry out a project together. [     ]
A.
reached
B.
had been reached
C.
was reached
D.
had reached
查看完整题目与答案