钢按用途分有哪些？
参考答案：
钢轨钢、锅炉钢、桥梁钢、船用钢、矿用钢等。
The number of people invited _______ one hundred, but only a small number of people ____ come.
A．are; have
B．is; has
C．are; has
D．is; have
急冷水循环过程中应注意哪些问题？
