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【单选题】
串联型稳压电路用复合管作调整管,是因为单管( ) A. 电流 I CM 不够小 B. 击穿电压不够高 C. 功耗 P CM 不够大 D. 电流放大系数不够大A.
电流 I CM 不够小
B.
击穿电压不够高
C.
功耗 P CM 不够大
D.
电流放大系数不够大
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举一反三
【单选题】A new technique_________, the yields as a whole increased by 20 percent.
A.
working out
B.
having worked out
C.
having been worked out
D.
to have been worked out
【单选题】________hard before, Tom is afraid of failing in the exam.
A.
Having been worked
B.
Not to have worked
C.
Having never worked
D.
Never have worked
【单选题】_______ , the girl worked in a hurry.
A.
Having swept the room
B.
Another room swept
C.
Having another room to sweep
D.
Having another room to be swept
【单选题】________ in the company for three years, Mark has become experienced in business negotiations. A) Having worked B) Have been working C) Have worked D) Worked
A.
Having worked
B.
Have been working
C.
Have worked
D.
Worked
【单选题】all day, I went to bed early.
A.
Working hard
B.
Worked hard
C.
Having worked hard
D.
To work hard
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