问题
选择题
Mr Wang and his students ____________ a lesson now.[ ]
A. are having
B. had
C. have
答案
答案：A
搜题请搜索小程序“爱下问搜题”
Mr Wang and his students ____________ a lesson now.[ ]
A. are having
B. had
C. have
答案：A
，如果某一闭合的10匝线圈，通过它的磁通量在0.1s内从0增加到1Wb，则线圈产生的感应电动势大小为[ ]