在放大器中，有电源滤波电容，若长时间使用后，电容失效，易引起（）干扰，在电视画面上表现为交流横黑白滚道。
参考答案：交流
治疗血虚型经行头痛的主方是（）
A．滋肾养阴，固冲止血
B．补肾益精，养血调经
C．活血化瘀调经
D．养血益气调经
E．补肾益气，调理冲任
They were singing and dancing to _____ their high spirits though it was very cold. [ ]
A. keep up
B. build up
C. bring up
D. pick up
