钢材的比重一般按（）计算。
A.6.55
B.7.85
C.8.90
参考答案：B
The stones are so heavy. How _____ they _____ to the top of the building without modern machines?
A．do; lift
B．did; lift
C．were; lifted
D．were; lift
锻件分模面不在同一平面时以及模膛中心和锤杆中心不一致时，错移力应如何平衡？
