问题
选择题
It's not good _____ loudly in class. [ ]
A. talk
B. to talk
C. talks
D. talked
答案
答案：B
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It's not good _____ loudly in class. [ ]
A. talk
B. to talk
C. talks
D. talked
答案：B
时（T为交流的周期），原线圈中的电流瞬时值为0.03A．变压器的原、副线圈的匝数比为（ ）
：3