问题
选择题
—I'd like to do somle volunteer work, but I'm not sure what I should do.
—You ______ give out food at the food bank. [ ]
A. should
B. must
C. could
D. need
答案
答案：C
搜题请搜索小程序“爱下问搜题”
—I'd like to do somle volunteer work, but I'm not sure what I should do.
—You ______ give out food at the food bank. [ ]
A. should
B. must
C. could
D. need
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