题干
He has lots of friend, only a few of ____ invited to his wedding.
A：whom
B：them
C：which
D：who
答案(点此获取答案解析）
B
A：whom
B：them
C：which
D：who
为相同的电流表，C为电容器，电阻
的阻值相同，线圈L的电阻不计。在某段时间内理想变压器原线圈内磁场的变化如图乙所示，则在
时间内
