有关压焊概念正确的是（）
A.对焊件施加压力但不能加热
B.对焊件施加压力且加热
C.对焊件施加压力，加热或不加
D.以上都有对
参考答案：C
Some people who don’t like to talk much are not necessarily shy; they _____ just be quiet people.
A．must
B．may
C．should
D．would
高炉停炉后进行炉体密封，目的是防止杂质进入炉内。
