长久使用的热水瓶底部有一层水垢，主要成分是 CaCO3 和 Mg(OH)2,某学校化学研 究小组的同学通过实验测定水垢中 CaCO3 的含量:取 200g 水垢，加入过量的稀盐酸，同时测量 5 分钟内生成气体的质量，结果如下表：
时间/min 1 2 3 4 5
质量/g 30 50 60 66 66
试回答下列问题：
(1)4 分钟后，产生的 CO2 不再增加，说明水垢中 CaCO3 (填已或未)反应完全?
（2）当反应完全时，CaCO3消耗的氯化氢为______g．
(3)该水垢中 CaCO3 的质量分数是多少?
Dogs are the best pets of humans. They come in all sizes. Some dogs are as small as a football, and others are as tall as a desk. Dogs’ fur (毛) is different, too. It can be long and soft, or smooth and hard. People don’t mind the kind of fur, because all dogs are good to hug.
请在字典中查一下这个词。
我喜欢甜食， 你知道的。
去年， 彼得在旅途中和许多人交了朋友。
我叫托尼· 史密斯， 史密斯是我的姓。
我们在课上回答问题时应该起立
Tea and coffee are two of the most popular drinks in the world. However, people usually like one more than the other. These drinks also have very different uses.
People in the office usually sit for most of the day when they work. But this is bad for a person’s health. When people sit for too long every day, they don’t move very much. So it is easy to start getting fat. Sitting too long is also bad for their work because it makes them want to sleep. When this happens, people may make more mistakes in their work or spend more time finishing their work. Companies need workers to be healthy, so how do they fix the problem?
