有A，B，C，D四种金属．将A与B用导线连接起来，浸入电解质溶液中，B不易腐蚀．将A，D分别投入等浓度盐酸中，D比A反应剧烈．将铜浸入B的盐溶液里，无明显变化．如果把铜浸入C的盐溶液里，有金属C析出．据此判断它们的活动性由强到弱的顺序是（   ）

阅读短文，判断下列句子是否正确。
    Ann went to Qingdao with her friends on her holiday. They went there by train. They went to the beautiful beach. The weather was sunny and hot. So they had great fun playing in the water.They ate lots of fresh fish for lunch. In the afternoon, they rode bikes. Jack fell off his bike and hurt his leg. So Jack stayed at the hotel and watched TV. On the second day, Ann took many pictures of the sea. And she bought some gifts for her parents. Anyway, they had a good time.

下列句子中没有语病的一句是

做一做．

冬天的早晨，池塘上常会出现大雾．这个现象发生的物态变化和吸、放热情况是（   ）