若单相桥式整流电路中有一只二极管已断路，则该电路（）。
A.不能工作
B.仍能正常工作
C.输出电压下降
D.输出电压上升
参考答案：C
具有清热燥湿、退虚热除蒸、解毒疗疮功效的药物是（）
A.银柴胡
B.苦参
C.黄芩
D.黄连
E.黄柏
Mary made coffee ____ her guests were finishing their meal. [ ]
A. so that
B. although
C. while
D. as if
