炸药在岩土，钢筋混凝土等介质内部爆炸时，对周围介质的作用成为爆破作用。
参考答案：对
Tom has two cousins, and ______ are engineers.
A．both of whom
B．both of them
C．none of them
D．either of them
升温钝化开始前，必须联系仪表将HS-204进行（）。
