问题
选择题
The boat _____ like a duck. [ ]
A. isn't look
B. don't look
C. doesn't look
D. doesn't looks
答案
答案：C
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The boat _____ like a duck. [ ]
A. isn't look
B. don't look
C. doesn't look
D. doesn't looks
答案：C
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