白头翁汤的功效是（）。
A.清热化湿，涩肠止痢
B.清热解毒，凉血散瘀
C.清热解毒，凉血止痢
D.清热凉血，消肿止痛
E.清热泻火，凉血止血
参考答案：C
It ________ be the postman at the door. It's only six o'clock. [ ]
A. mustn't
B. can't
C. won't
D. needn't
什么是空气的温度？有几种表示方法？
