充装系数是标准规定的气瓶（）允许充装的最大气体重量。
参考答案：单位水容积
With a lot of difficult problems________,the newlyelected president is having a hard time. [ ]
A. settled
B. settling
C. to settle
D. being settled
区别甾体皂苷和三萜皂苷用( )
A．三氯乙酸反应B．Molish反应C．中性乙酸铅反应D．IR光谱E．吉拉尔(Girard)试剂
