民用液化气收率单位％是（）。
A、摩尔百分比
B、体积百分比
C、质量百分比
D、比重百分比
参考答案：C
Some people won't realize the importance of their health _______ they have lost it. [ ]
A. after
B. when
C. until
D. as
分类法的基本生产成本明细账是按（）设置。
A.产品品种
B.产品批别
C.产品类别
D.产品生产步骤
