硅整流器中每个二极管在一个周期的连续导通的时间为( )。
A. 1/2周期
B. 1/3周期
C. 1/6周期
D. 1/4周期
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交流发电机是利用硅二极管的单项导电特性把交流电转化为直流电。
A. 对
B. 错
---Who’s that? ---______ is Tom.
A. It
B. He
C. She
D. Her
Give ______ some boxes.
A. they
B. their
C. them
D. theirs
These are ______ chairs.
A. students
B. students'
C. the student's
D. students's