题干

下列说法中正确的是                 (  )                           

A:离子晶体中每个离子周围均吸引着6个带相反电荷的离子

B:金属导电的原因是在外电场作用下金属产生自由电子,电子定向移动

C:分子晶体的熔沸点很低,常温下都呈液态或气态

D:原子晶体中的各相邻原子都以共价键相结合

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D

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    Jia Zuosheng, 27, used to work as a security guard (保安) at the library of Tsinghua University. But a few months ago, he became a college student in Lishan College in Shandong and he studies math there now. When hearing this news, many people were surprised. On school opening day, many reporters waited outside the school gate to interview him.

    “I was born in a poor village in Shandong Province," said Jia. "Our village has never had a college student. Most boys work in town after growing up. I failed the National College Entrance Exam(高考)twice. Then I went to Beijing to find jobs. In the following years, I went on studying by myself while working.”

    At the end of 2009, Jia found a job as a security guard at the library of Tsinghua University.“I cherished (珍惜) the job very much because it gave me a good chance to read books," Jia said.“I usually worked at night so I had plenty of time to study in the daytime.” When he had problems that he couldn't work out, Jia asked the students at Tsinghua for help. "My dream is to be a college teacher. So I need further education. That's the reason why I took the National College Entrance Exam again," Jia said. “I wish to educate students with my knowledge and love and help them enjoy true, kind and beautiful things.”

    Jia's mother said Jia has always been independent(独立的)and knows what he wants. But she has other worries. "It's difficult to find such a good job at present as a library guard in Tsinghua University. I'm not sure if this is a right decision.” “I will never regret(后悔),”said Jia. "Everyone will have a new start. It's the end, and the beginning.”