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【单选题】
The passage implies that______.A.
LED bulbs are still expensive at present
B.
the task of making LED the main source of artificial light is too difficult
C.
LED traffic lights are used everywhere in the world
D.
in order to fulfill the task of making LED the main light source, lightbulb makers have to work together with semiconductor manufacturers
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【单选题】. 戴维南定理指出:任何一个线性有源二端网络对外电路来说都可以用一个电压源与电阻的串联模型等效代替,其中串联电阻等于该网络中所有的电压源代之以(),电流源代之以()后所得无源二端网络的等效电阻。
A.
断路、短路
B.
断路、断路
C.
短路、断路
D.
短路、短路
【单选题】There are four factories in our institute, _______.
A.
with which having over 100 workers
B.
each having over 100 workers
C.
which there are over 100 workers
D.
with each that has over 100 workers
【单选题】Our town has dozens of factories, ____ several sawmills.
A.
included
B.
are including
C.
are included
D.
including
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