问题
选择题
在化学反应中，催化剂（ ）
A．质量减小
B．在反应后化学性质发生了变化
C．质量增加
D．能改变其它物质的化学反应速率
答案
由催化剂的概念可知，催化剂能够改变化学反应速率，其质量和化学性质在化学反应前后保持不变．故A、B、C说法错误．
故选D．
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在化学反应中，催化剂（ ）
A．质量减小
B．在反应后化学性质发生了变化
C．质量增加
D．能改变其它物质的化学反应速率
由催化剂的概念可知，催化剂能够改变化学反应速率，其质量和化学性质在化学反应前后保持不变．故A、B、C说法错误．
故选D．
Once upon a time there were two brothers who lived near each other. One day, they had a 16 because of some small things. And neither was willing to 17 each other. One morning, there was a knock at door of the elder brother. He 18 it and found a man standing beside the door. “I’m a carpenter(木匠). I’m 19 a few days’ work. Perhaps you would have a few small jobs I could help with.” “Yes,” said the elder brother. “I do have a job for you. 20 at that farm across the small river. It is my younger brother’s. We had a quarrel, so I won’t like to see his 21 any more. I want you to build me a 8-foot 22. ” The man said, “I think I understand the situation. Don’t worry. I’ll be able to do a job that makes you 23” So the elder brother was very glad and left for the town nearby. In the evening, the carpenter had just 24 his job when the elder brother returned. But he was 25 to find, instead of a fence, before him, stood a 2 6, which went from one side of the river 27 the other! On the other 28 of bridge, was his younger brother. “Do you know the name of the bridge?” The carpenter asked. “No,” the elder brother was 29 “OK, I can tell you. Its name is understanding and 30,” the carpenter smiled. Suddenly they began to understand 31. Surely, between two brothers there should be a bridge rather than a 32. Standing on the bridge, they 33each other’s hands with 34 in their eyes. “Could you stay another few days? I’ve a lot of other work for you,” said the elder brother. “I’d love to 35 on,” the carpenter said. “But I have many more bridges to build.”
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