压力拱理论稳定条件：（），适用条件：能够形成压力拱，即洞室上方有足够的厚度且有相当稳定的岩体。
参考答案：沿着拱的切线方向仅作用着压力
用所给词的适当形式填空。
1. _______ (judge) from his _______ (express), we know that he has _______ (success).
2. "I take ____ in your good deeds," the teacher said _______ to his pupils. (proud)
3. _______ (luck), the _______ (survive) have been rescued.
4. I'm _______ (terrible) sorry; did I hurt you?
5. In the letter we offered our sincere _______ to her on her marriage. (congratulate)
下列物质中，不能与氯化铜溶液发生置换反应的是（ ）
A．镁
B．锌
C．铁
D．银
