四环素类抗生素结构中（）极性大，影响药物在体内的吸收及稳定性。
A.4位二甲胺基
B.6位羟基
C.3位羟基
D.1位羰基
参考答案：B
In order to reduce air pollution, many people want a total _____on the playing of firecrackers (鞭炮)in many cities during the Spring Festival.
A．presentation
B．promotion
C． prohibition
D．performance
简述芳香化湿药的主要药理作用。
