问题
选择题
进入秋冬季节，更应注意安全，要避免含碳燃料不充分燃烧产生的一氧化碳（化学式CO）而导致悲剧发生．一氧化碳中碳元素的化合价是（ ）
A．-2
B．+4
C．+1
D．+2
答案
设化合物CO中C元素化合价为n价，依化合物中各元素化合价代数和为零的原则有n+（-2）=0，
解之得n=+2；
故选D．
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进入秋冬季节，更应注意安全，要避免含碳燃料不充分燃烧产生的一氧化碳（化学式CO）而导致悲剧发生．一氧化碳中碳元素的化合价是（ ）
A．-2
B．+4
C．+1
D．+2
设化合物CO中C元素化合价为n价，依化合物中各元素化合价代数和为零的原则有n+（-2）=0，
解之得n=+2；
故选D．
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| Yesterday my grandfather told me about his early days. 1 he left school, he found a job in a post office. He worked hard there. Soon he had more money than his friends because of his hard work. It seemed that he would have a 2 future. When he was 25 years old, however, he began to be 3 his job. He wanted a more exciting one, so he left the post office. Two months 4 , he found a new job in a big 5 . Workers in this company 6 traveled a lot. At first he really enjoyed the traveling. But after a year, he began to 7 it. He had to move around and he was always in a car or on a train. The 8 thing was that he couldn't make any new friends. Even so, his boss was not satisfied with him. Two years later he 9 the company. He was so 10 at that time that he sold his house. He had to accept a part-time job in a 11 shop. He was surprised to find that he loved it! He made new friends every day and he 12 reading books. Three years later, he 13 the shop owner's daughter. Soon they had their first child. In the next ten years, they had another three 14 and four more book shops! He became very rich indeed. "Life is wonderful," he told me."The most 15 thing is that you should always try your best. Never give up!" | ||||
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