下列计算正确的是

改错题

Dear Editor,

    I am writing tell you about the discussion we've had about whether it is necessary of middle school students to have mobile phones. Most students think this is more convenient for them to keep in the touch with their parents and classmates. And what's much, it's a fashion. However, most teachers think middle school students are not old enough to control them. It is a waste of time for students to play games and sending messages on their mobile phones. Therefore, it is easy to make students contact with each other. In my opinion, following the fashion was understandable. But as middle school student, we should put all our energy into our study.

Yours truly,

Mary

根据我国多民族的实际情况，我国实行民族区域自治制度。自治权是民族区域自治制度的核心内容，是自治机关根据本地方实际情况贯彻执行国家法律，政策，自主管理本民族自治地方内部事务的权力，内容涉及政治、经济、文化和社会生活各个方面。下列对民族区域自治理解正确的是（    ）

①只有民族自治地方的人大及其常委会才能行使自治权

②有利于巩固和发展平等团结互助和谐的新型民族关系

③消除了我国各民族间经济、文化等发展不平衡的状况

④满足了各少数民族人民积极参与国家政治生活的愿望

下表是某人的血浆、原尿、尿液成分的比较（单位：g/100ml）。其中的丙是（     ）