题目

第三部分：阅读理解（共20小题；每小题2分，满分40分） 阅读下面短文，从每题后所给的四个选项A、B、C、D中，选出最佳选项，并在答题卡上将该项涂黑。Without proper planning, tourism can cause problems. For example, too many tourists can crowd public places that are also enjoyed by the inhabitants of a country. If tourists create too much traffic, the inhabitants become annoyed and unhappy. They begin to dislike tourists and to treat them impolitely. They forget how much tourism can help the country’s economy. It is important to think ab有X、Y、Z三种元素：（1）X、Y、Z的单质在常温下均为气体；（2）X单质可以在Z的单质中燃烧，生成物为XZ，火焰呈苍白色；（3）XZ极易溶于水，在水溶液中电离出X+和Z-，其水溶液能使蓝色石蕊试纸变红；（4）每2个X2分子能与1个Y2分子化合成2个X2Y分子，X2Y常温下为液体；（5）Z单质溶于X2Y中，所得溶液具有漂白性。试写出其元素符号：X__，Y__，Z__，化合物的分子式：XZ__，X2Y__。