题目

用32P和35S标记的噬菌体分别侵染细菌，经短时间保温后，用搅拌机搅拌，然后离心得到上清液和沉淀物，检测上清液和沉淀物中35S和32P的放射性。据图判断下列叙述错误的是（ ）A.图 2 中用35S、32P分别标记噬菌体的蛋白质、DNA，标记元素所在部位分别对应于图1中的④、①B.图 2 中的⑦⑧分别代表搅拌、离心过程，其中⑧的目的是使吸附在细菌上的噬菌体与细菌分离C.35S 标记的噬菌体侵染实验中，搅拌时间过短，沉淀物中的放射性很高D.35 S 标记的噬菌Nuclear power's(核能的) danger to health, safety, and even life itself can be described in one word; radiation(辐射). Nuclear radiation has a certain mystery about it, partly because it cannot be detected (探测) by human senses. It can't be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can't detect them, sense them, without a radio receiver. Similarly, we can't sense radioactivity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things. At very high levels, radiation can kill an animal or human being completely by killing masses of cells (细胞) in important organs (器官). But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not be significant. This is the case when only a few cells are hit, and if they are killed completely. Your body will replace the dead cells with healthy ones. But if the few cells are only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in an unusual way. They can grow into cancer. Sometimes this does not show up for many years.This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the knowledge of the person at the time that damage has occurred. A person can be irradiated(放射治疗) and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or easy to get serious illness as a result of radiation absorbed by its grandparents. Radiation can hurt us. We must know the truth.1.According to the passage, the danger of nuclear power lies in __________.A. nuclear mystery B. radiation detectionC. radiation level D. nuclear radiation2.Radiation can lead to serious results even at the lowest level ________.A. when it kills few cellsB. though the damaged cells can repair themselvesC. if it damages few cellsD. unless the damaged cells can reproduce themselves3.Radiation can hurt us in the way that it can _____.A. kill large numbers of cells in main organs so as to cause death immediatelyB. damage cells which may grow into cancer years laterC. affect the healthy growth of our younger generationD. lead to all of the above results4.Which of the following can be best inferred from the passage?A. The importance of protection from radiation cannot be overemphasized (过分强调).B. The mystery about radiation remains unsolved.C. Cancer is mainly caused by radiation.D. Radiation can hurt those who do not know about its danger.