升麻的功效是( )
A．清热解毒B．息风止痉C．燥湿止带D．行气宽中E．解表除烦
参考答案：A
Many people are worried about the pollution in big cities and rainforest [ ]
A. disappear
B. disappeared
C. disappearing
简述离心泵发生汽蚀的原因有哪些？
