下列离子方程式中正确的是（   ）

      An Englishman was showing a foreign visitor around London. “What’s that strange building?” asked the visitor. “That's the Tower of London.” “I see. How long did it take to build it?” “About 500 years.” “In my country we can build it in five months,” Shortly after that they came to St. Paul's Cathedral(大教堂). “Very interesting!” said the visitor. “How long did it take to build it ?” “Near forty years.” said the Englishman. “In my country we can finish it in forty days at most,” said the visitor. This went on all day.
      They visited most of the best known buildings in the city. Every time they saw a new one, the visitor asked what it was and how long it took to build it. Then he said that they could do the same thing much faster in his country.
      At last the Englishman got angry with the visitor though he tried not to show it. Several days later they came to the House of Parliament(议会)and the visitor asked his usual question, “What is that?” The Englishman answered, “ I have no idea. It wasn't there last night.”

如图是人在一个标准大气压下的一次平静呼吸过程中肺内气体的变化曲线图，下列表述正确的是（　　）

阅读短文，填入适当的单词，使其内容通顺，每线一词，首字母已给。

    Danny's father is a firefighter. He works at fire station. He's very brave. He h____ short yellow hair. He is tall and thin. His c____ are orange. He likes putting out the f____. Danny's mother is a t____. She works in a school. Her students like her very much. She has a b____ and two dresses. They are purple.

    They are nice. She likes playing games with her students. She is a good teacher.

根据如图所示某牙膏商标上的部分文字，用化学用语填空：

（1）图中一种金属元素的符号　____ ；

（2）n个硝酸根离子的符号____ 　；

（3）碳酸钙高温分解反应的化学方程式____ ．