亲脂性存机溶剂提取生物碱,使用前先应对药材进行何种特殊处理( )
A.粉碎药材
B.少量酸水湿润药材
C.少量碱水湿润药材
D.烘干药材
E.煮沸药材
参考答案:C
One of the boys ________ doing __________ homework in the classroom.
A. is; their B. are; his C. is; his
从电网向工作机械的电动机等供电的电路是
A.主电路
B.控制电路
C.保护电路
D.信号电路