题目

以下化学反应的离子方程式书写正确的是（   ） A．NH4HCO3溶于过量的NaOH溶液中：HCO3— +OH— ＝ CO32—+ H2O B．将少量金属钠放入冷水中：Na + 2H2O ＝ Na＋+2OH－+ H2↑ C．FeCl3溶液与Cu的反应：Cu + Fe3+ ＝ Cu2+ + Fe2+ D．FeSO4溶液中加入H2O2：2Fe2+ + H2O2+ 2H+ ＝ 2Fe3+ + 2H2O  答案：D解析:选项A中漏掉NH4+与+OH—反应的离子方程式，A错误；选项B中电荷不守恒，B错误；FeCl3溶液与Cu的反应：Cu +2 Fe3+ ＝ Cu2++ 2Fe2+，C错误。 Tigers are strong and dangerous animals. But now they are in danger.In the past, there were eight kinds of tigers in the world. But during the 20th century, only five were left. The number of Siberian tigers (东北虎) was about 300, but now it is less than 22. They’re in danger of dying out.（灭绝） If the government does nothing, we won’t be able to see them in ten to twenty years.In order to stop people from hunting and killing wild tigers, and in order to make wild tigers more, the World Wildlife Fund (世界自然基金会) has started a program (项目) recently (最近). China and twelve other countries joined it.However, it’s not enough. Remember that nature is a food chain (链). If we hurt and kill too many wild deer and pigs, wild tigers will die out because of hunger (饥饿). So the most important thing is to save the animals that tigers eat. In order to protect the wild tigers, we need call on (号召) more people to stop eating, hunting and killing wild animals.根据短文内容，选择正确答案。【1】 During the 20th century, _______ kinds of wild tigers died out.A. 3 B. 5 C. 8 D. 20【2】The number of the wild Siberian tigers reduced (减少) about _______.A. 5% B. 22 C. 93% D. 30%【3】Wild tigers will be in danger of dying out without _______.A. pigs B. deer C. people D. A and B【4】Which of the following statements is NOT true?A. There are less than 22 wild Siberian tigers now.B. There are twelve countries in the World Wildlife Fund.C. Wild tigers mainly feed on pigs and deer.D. It’s our duty to protect the wild tigers.【5】The passage mainly tells us _______.A. why and how do we protect the wild tigersB. the government does everything they could to protect the wild tigersC. the wild tigers will die out in ten to twenty yearsD. the most important thing is to save the animals that tigers eat