用NA表示阿伏加德罗常数的值，下列叙述正确的是（ ）
A．室温下，21.0g乙烯和丁烯的混合气体中含有的碳原子数目为1.5NA
B．标准状况下，2.24L Cl2与过量稀NaOH溶液反应，转移的电子总数为0.2NA
C．25℃时，pH=13的1.0L Ba（OH）2溶液中含有的OH-数目为0.2NA
D．标准状况下，22.4L 甲醇中含有的氧原子数为1.0NA
A、乙烯和丁烯最简式相同，只需要计算21gCH2中的碳原子数即可，21gCH2物质的量为
=0.15mol，含有的碳原子数目为1.5NA，故A正确；2.1g 14g/mol
B、标准状况下，2.24L Cl2物质的量0.1mol，与氢氧化钠反应，氯气自身氧化还原反应，转移电子数为0.1NA，故B错误；
C、溶液中水电离生成氢氧根离子，pH=13的1.0L Ba（OH）2溶液中含有的OH-数目大于0.2NA，故C错误；
D、标准状况下，甲醇不是气体，22.4L 甲醇不是1mol，故D错误；
故选A．
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| Recently I was walking in town when I saw a group of school students in uniform. I was shocked to see that the girls' skirts were very short and they were wearing a lot of make-up. The boys looked very untidy. Their shirts were dirty and some of them even had their shirtfronts open. I noticed too that some of the students had pierced ears and-noses, which I don' t think should be allowed at school. And the other day, I was riding on the subway when I saw some boys from a local school. I know they were from this school because they were wearing the same uniforms my children. Instead of sitting quietly, these boys were making a lot of noise, chewing gum in an ugly manner, and using bad language. All the other passengers were looking at them and wondering how it was possible for these boys not to have any self-respect (自尊). They were also giving their school a very bad image (形象), which is shameful (羞耻的). I am a mother of two teenagers at school and I am worried that my children also behave like this and I do not know about it. Do school students know what is allowed and what is not allowed when they are wearing their school uniform? I think the school should be stricter with the students. And I think all students should be taught how to be polite. | ||||||||||
请依据该家长观察到的一些学生的行为，完成下列表格中的句子。
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