交叉配血的血样标本必须是输血前几天内的？（）
A.2天内
B.3天内
C.5天内
D.1周内
参考答案：B
30. Only those who have experienced hardship ____ well aware of what happiness means.
A．can they be
B．they can be
C．can be
D．they can
一般新建机房净高为（）.
A.4500～4000mm
B.3600～3300mm
C.3500～3300mm
D.3300～3200mm
