普通混凝土干表现密度为（）㎏／m3。
A.2000～2800
B.2100～2850
C.2200～2900
D.2200～2950
参考答案：A
At first ___ , the bag seems made of real leather, but actually it is just an imitation.
A．sight
B．look
C．appearance
D．view
铁水中锰硅比为（）时，对冶炼操作有利。
A、0.5－0.7
B、0.8－1.0
C、1.0-1.2
D、0.3-0.5
