B．光的干涉现象
C．光的衍射现象
D．光的色散现象
答案：A
Although the police thought he was the most likely one, _____ they had no exact proof about it, they could not arrest him.
A．when
B．until
C．before
D．since
A．10：3
B．3：10
C．3：10
D．10：3
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