钣金工常用的连接方法有榫连接、铆接、螺栓连接和（）。
参考答案：焊接
—Linda hasn't shown up yet.
—It's strange. She _________. [ ]
A. could
B. might
C. must have
D. should have
煤矿生产规模达到300万吨以上对技术管理人员有何要求?
