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　　Passage 7

　　In our daily life， few people notice the fact that warm water freezes more quickly than cold. Sir Francis Bacon said that almost four hundred years ago. But few people believed him till 1970. In that year Canadian Scientist George Kell proved the English scholar was right. Dr. Kell filled an open bucket with cold water. He filled another with warm water. He exposed both to the same low temperature. The warm water froze first.

　　The lack of covers on the buckets was the secret. Some of the warm water changed to vapor. It evaporated （蒸发） into the air. This meant that less of the warm water was left to freeze. And so the warm water froze faster than the cold water even though it had a greater temperature drop to make.

　　1. Sir Francis Bacon was ______.

　　A. an American experimenter B. a Canadian scientist

　　C. an English scholar D. an Australian writer

　　本句that 引导的是同位语从句。

　　常见的同位语从句的引导词：idea、fact、news、fear、belief、doubt、proof、evidence等。

　　答案：C

　　2. Dr. Kell's buckets were both ______.

　　A. filled with water B. left uncovered

　　C. exposed to the same temperature D. All of the above

　　another指的是another bucket. expose 暴露 uncovered 无盖的 答案：D

　　3. The second paragraph tells why ______.

　　A. Dr. Kell was studying water

　　B. the warm water froze first

　　C. Dr. Kell used buckets in his work

　　D. water freezes in underground pipes

　　underground 地下的 答案：B

　　4. No water vapor would have escaped into the air if the bucket had been ______.

　　A. warmed B. covered C. shaken D. filled

　　if the bucket had been 虚拟语气 答案：B

　　5. The cold water froze more slowly because ______.

　　A. salt was added to it B. its bucket was smaller

　　C. there was more of it left D. the air near it was moving 答案：C

　　做阅读理解时，要抓紧时间，对于简单的题目（如：常识题）不要花太多时间，对于较难的题目要对照原文多加分析。

　　下次课的主要内容是Passage 8和Passage 9，预习并找出两篇文章的关键句。