炸药爆炸必须具备哪三个基本要素，为什么？
参考答案：
化学反应的放热性、生成大量气体产物、化学反应和传播的快速性，是炸药爆炸的三个基本特征。炸药是在一定条件下，能够发生快速化学反应，放出能量，生成气体产物，并产生爆炸效应的化合物或混合物。在平常条件下，炸药是比较安定的物质，但一旦外界给予足够的活化能，使炸药内各种分子的运动速度和相互间的碰撞力增加，使之发生迅速的化学反应，炸药就会丧失安定性，从而引起爆炸。
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| One day a woman got into her car and started driving home after work. Just at that time, she saw a 1 car behind her. The driver was a 2 . When she turned left, the yellow car turned left. When she turned 3 , the yellow car turned right, too. When she stopped at the traffic lights, the yellow car stopped 4 her. The woman was 5 , so she drove quickly to 6 . When she arrived, she was very 7 to see that the yellow car stopped behind her again. But she felt 8 because she saw a policeman standing outside the police station. She jumped out of her car at once and 9 to the policeman. She asked the policeman to arrest (逮捕) the man in the yellow car, then the policeman walked to the man. The man didn't run away. He just 10 and said to the woman,"I want to give this purse back to you. I think you dropped it on the street." | |||
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