The fine was for the company's ___ of the air near its plants.
A.pollute
B.pollutant
C.pollution
D.polluted
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The contraction of muscles uses energy and releases heat.What is the meaning of the ‘release’in the sentence?
A. to let somebody or something come out of a place where they have been kept or trapped
B. to express feelings
C. to free somebody from a duty
D. to make something less tight
There are hundreds of ___ spiders and snakes.
A.prison
B.poison
C.poisonous
D.prisoner
运算放大器的组成部分有（）。
A. 输入级
B. 发射极
C. 中间级
D. 输出级
E. 偏置电路
运算放大器接成负反馈电路，则此运算放大器就工作在线性区。运算放大器工作中线性区的特点有（）。
A. 虚地
B. 虚短
C. 虚断
D. 虚输入
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