题干
Jim was late for class yesterday because he had accident on his way to school.
A：an
B：a
C：the
D：/
答案(点此获取答案解析）
A
个完全相同的灯泡a、b和c分别与电阻R、电感L和电容C串联，当电路两端接入220V、50Hz的交变电压，三个灯泡亮度恰好相同。若保持交变电压大小不变，将频率增大到60Hz，则将发生的现象是（ ）