路中两条双黄色虚线是什么标线？（） A．单向分道线 B．可跨越分道线 C．潮汐车道线

Nuclear power’s danger to health, safety, and even life itself can be summed up in one word: radiation.

Nuclear radiation has a certain mystery about it, partly because it cannot be detected 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 radio activity 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 outright by killing masses of cells in vital organs. 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 outright, 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 a deformed 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 victim being aware at the time that damage has occurred. A person can he irradiated and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or liable to serious illness as a result of radiation absorbed by its grandparents.

Radiation can hurt us. We must know the truth.

Which of the following can be best inferred from the passage（）

A. The importance of protection from radiation cannot be over-emphasized

B. The mystery about radiation remains unsolved

C. Cancer is mainly caused by radiation

D. Radiation can hurt those who are not aware of its danger

下列说法中，正确的是

A．SO₂水溶液能导电，所以SO₂是电解质

B．Na₂CO₃既是钠盐又是碳酸盐

C．向醋酸溶液中加入少量氢氧化钠固体，由于发生中和反应，溶液的导电能力降低

D．NaCl溶液能导电所以NaCl溶液是电解质

用激光在磁性材料或相变材料上实现信息的存储和擦除是（）光盘。

A、可擦式

B、只读式

C、一次写入式

D、5.25英寸式

沈庆，男，22岁，初中没毕业，性格内向、懒散、缺乏上进心。沈庆幼年时，父母离异，他随父亲生活。之后，父亲再婚，继母带来一位女儿，父亲和继母都没有工作，一家四口靠低保度日，生活十分困难。沈庆在上小学时，学习还不错，升初中后，由于父亲和继母对他不管不问，学习成绩一落千丈。他还天天逛网吧，在网吧结交了一群“哥们”，由于没钱上网，他负责看管“哥们”的财物，以此从“哥们”那边蹭上网时间或者和“哥们”一起上网。自从结交了一群“哥们”后，他经常彻夜不归。初二第二个学期，他对学习失去了兴趣，结束了读书生涯，仅拿到初中肄业证书，连劳动手册也无法办理，他也不急着找工作。

[问题]

上述案例中，沈庆面临的问题主要有哪些

在中华人民共和国境内从事（）等活动，适用《无公害农产品管理办法》。

A.无公害农产品生产

B.产地认定

C.产品认证

D.无公害农产品监督管理