合金结构钢按热处理方法可分为哪几种？
参考答案：
渗碳钢、调质钢、氮化钢。
计算：（-3x2y）2•（-2xy）=______．
Over the past 20 years, the Internet has helped change our world in ___________ way or another for the better.[ ]
A. any
B. one
C. every
D. either
