跨度为8m的预制阳台脱模起吊时混凝土强度允许值应达到（）。
A.40%
B.50%
C.65%
D.75%
参考答案：D
. She is in a poor ____ of health, which worries her mother a lot.
A．position
B．situation
C．state
D．Condition
什么材质的板不适用于剪板机？
