薄层色谱法测定苯甲酸及其钠盐时，样品酸化后，用于提取苯甲酸的是
A.己烷
B.乙醇
C.正己烷
D.乙酸
E.乙醚
参考答案：E
I'll go to the library as soon as I finish what I ________.[ ]
A. was doing
B. am doing
C. have done
D. had been doing
利用收益还原法评估不动产价格时，首先，计算待估不动产的( )，然后用综合还原率还原，求取不动产的收益价格。
A．还原率
B．总价值
C．折旧额
D．总纯收益
