( )是计算评价指标的基础。
A．流动资金B．投资现金流量C．净现金流量D．自由现金流量
参考答案：C
The woman was about to open the door ____________ she heard a strange sound from inside.
A．as
B．while
C．when
D．then
判断前置胎盘最主要的方法是进行肛查
