检验钢材质量的指标有哪几项？
参考答案：
对于有明显屈服点的钢材其指标有：屈服强度、抗拉强度、伸长率、冷弯性能。对于无明显屈服点的钢材只测定后三项。
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She seemed ________ the book before, but she said she had never.
A．to read
B．to have read
C．to be reading
D．reading
容积式泵需要在开泵之前关闭出口阀，离心泵则相反。
