生命科学研究常利用同位素标记特定的化合物追踪或显示物质运行和变化过程。下列各项所选择使用的同位素及相关结论不正确的是[ ]
A．同位素：35S 应用：标记噬菌体蛋白质，其子代噬菌体中不应该含35S
B．同位素：15N 应用：标记DNA分子，证明DNA分子半保留复制方式
C．同位素：32P 应用：标记噬菌体的DNA，证明DNA是遗传物质
D．同位素：32P、35S 应用：用含这两种同位素的培养基去培养噬菌体进行标记
答案：D
| 阅读理解。 |
| New rules and behavior standards (标准) for middle school students came out in March. Middle school is going to use a new way to decide who the top students are. The best students won't only have high marks. They will also be kids who don't dye (染) their hair, smoke or drink. The following are some of the new rules. Tell the truth. Have you ever copied someone else's work on an exam? Don't do it again! That's not something an honest (诚实的) student should do. If you have played computer games for two hours in your room, don't tell your parents you have done homework. Do more at school. Good students love animals and care for other people. April is Bird-Loving Month in China. Is your school doing anything to celebrate (庆祝)? You should join! That way, you can learn more about animals and how to protect them. When more people work together, it makes it more fun for everyone. Have you ever quarreled (争吵) with your teammates when your basketball team lost? Only working together can make your team stronger. Be friendly to the people you are with. Try to think of others, not only yourself. Be open to new ideas. Have you ever thought that people could live on the moon? Maybe you'll discover Earth II someday. Don't look down on (轻视) new ideas. Everyone's ideas are important. You should welcome them, because new ideas make life better for everyone. Protect yourself. Has someone ever taken money from one of your classmates? Don't let it happen to you. If you have to go home late, you should let your parents know. Use the Internet carefully. The Internet can be very useful for your studies. But some things on the Internet aren't for kids, so try to look at Web pages that are good for you. You can use the Web for fun or homework. Can't you find any good Web sites for children? Here are some: http://kids.easyday.com http://www.chinakids.net.com http://www.cycnet.com |
| 1. An honest student should _____. |
| A. tell the truth even when he is wrong. B. copy someone else's work in an exam. C. try to think of others,not only yourself. D. quarrel with your teammates when your basketball team loses. |
| 2. The main idea of the fourth paragraph is about _____. |
| A. making your team stronger B. being strict with others C. learning from each other D. working together with others |
| 3. Paragraph 5 tells students to _____. |
| A. live on the moon B. discover Earth Ⅱ C. look down on new ideas D. be open to new ideas |
| 4. Good Web sites for children can _____. |
| A. be a waste of time B. make life much easier C. help them with their studies D. do homework for them |
| 5. The school new rules will help kids by telling them _____. |
| A. how they can study well B. what is right and what is wrong C. what they should do at school D. how they can protect themselves |