(1)下列烷烃的沸点由高到低排序正确的是? ( )①2-甲基戊烷 ②正己烷 ③正庚烷 ④3-甲基己烷
A. ①②③④
B. ③④②①
C. ④③①②
D. ④②③①
查看答案
烷烃的卤代反应能否进行,由该反应的反应热决定。
A. 对
B. 错
烷烃的熔点不仅与分子间作用力有关,还与分子的对称性有关,分子式相同的异构体,分子的对称性越高,分子的熔点越高。
A. 对
B. 错
65. From the age of 15, young people can become British Red Cross volunteers (英国红十字会志愿者) – but that doesn’t mean you can’t start earlier.We have set up this age rule for many reasons. But the fact is that we’d love you to learn more about our work at the Red Cross right now—and perhaps start preparing for your future volunteering role.We have lots of activities to keep you involved right now.
man 5 passwd 含义是?
A. 显示 passwd 命令的使用方法
B. 显示 passwd 文件的结构
C. 显示 passwd 命令的说明的前五行
D. 显示关于passwd的前五处说明文档。