金瓷冠不透明瓷厚度一般为（）
A.0.1mm
B.0.2mm
C.0.3mm
D.0.5mm
E.2mm
参考答案：B
Mother keeps telling me not to waste money because money is difficult ________ nowadays.
A．earned
B．earning
C．to earn
D．to be earned
水泥混凝土路面的模板应在混凝土抗压强度不小于( )MPa时方可进行拆除。
A．8
B．10
C．15
D．30
