We’ve heard about radiation from the damaged nuclear reactors in Japan reaching American shores. Experts say so far there is no reason to worry, and point out that we meet radiation every day. Where and how? NPR’s Renee Montagne posed that question to Peter Caracappa, a radiation safety officer and professor of nuclear engineering.

MONTAGNE: How many things emit radiation?

Dr CARACAPPA: Well, radiation and radioactive material is a part of nature. So everything that’s living has some amount of radiation coming from it—a very small amout. Plus there’s radiation in the ground and the air.

So the extremes are uranium in the soil to bananas?

Yes.

By the way, why do bananas have radiation?

Bananas have a lot of potassium(钾). And a small amount of potassium naturally is called potassium 40, which is radioactive

What’s the difference between radiation that’s harmful and not harmful?

Well, the term radiation can apply to a lot of different things. But the harmful radiation is ionizing(离子)radiation. It has enough energy that it can make chemical changes in material. We could get ionizing radiation from an X-ray, for example. It’s the kind of radiation that causes cancer.

The broader definition of radiation includes a lot of things that we call non-ionizing radiation. That includes everything like radio waves and visible light and your microwave.

So what then is the largest contributor of ionizing radiation?

For the natural sources of ionizing radiation, actually the biggest chunk of that tends to come from radon(氡), which is a radioactive material that is present in the air. It can become a concern when it builds up in low-lying areas of homes like basements.

Would it be fair to say that most people do not need to worry about the danger of being exposed to radiation?

I would say that the everyday exposure to radioation that we meet contributes an extremely tiny risk to our life or to our health compared to all of the other risks that we meet in our day-to-day life.

1.We can infer from the first paragraph that radiation is______.

2.The passage may be _______.

3.Whether radiation is harmful or not depends on______.

4.The purpose of writing this passage is to _______.

It is difficult for doctors to help a person with a damaged brain. Without enough blood, the brain lives for only three to five minutes. More often the doctors can' t fix the damage. Sometimes they are afraid to try something to help because it is dangerous to work on the brain. The doctors might make the person worse if he operates on the brain.
Dr. Robert White, a famous professor and doctor, thinks he knows a way to help. He thinks doctors should make the brain very cold. If it is very cold, the brain can live without blood for 30 minutes. This gives the doctor a longer time to do something for the brain.
Dr. White tried his idea on 13 monkeys. First he taught them to do different jobs, then he operated on them. He made the monkeys' blood go through a machine. The machine cooled the blood. Then the machine sent the blood back to the monkeys' brains. When the brain' s temperature was 10°C, Dr. White stopped the blood to the brain. After 30 minutes he turned the blood back on. He warmed the blood again. After their operations the monkeys were like they had been before. They were healthy and busy. Each one could still do the jobs the doctor had taught them.
【小题1】The biggest difficulty in operating on the damaged brain is that _______.

---That must have been a terrible experience．

---Yeah．I      in the damaged car，unable to move．

A．was stuck    B．have been stuck    C．am stuck  D．had been stuck．

—That must have been a terrifying experience.

—Yeah. I _____ in the damaged car, unable to move.

The telephone rang in the police station at Richmond, California, USA. “Police station？ A train for Santa FE collide（碰撞）with a（n）　31　at the McDonald Street Crossing. Please go there at once, with an ambulance too. A man is badly injured，” said a（n）　32　voice of a young woman.

“Just a minute, we’ll come　33　. Please stay there and wait，” answered the policeman.

Within a minute, a police car and an ambulance　34　. Soon they got to the　35　, but only to　36　everything was fine. No collision, no　37　man.

“What a dirty trick！” said the policeman　38　. “We must find out that mischievous（恶作剧的）　39　and.”

They had not been able to say anything about a punishment　40　they heard the whistle of a train: the train was nearing them quickly. All　41　a sudden, a truck appeared. It came fast towards them, too. 　42　it was passing the crossing, it suddenly refused to move on. Right then and there, before the eyes of all the people present, the train collided with the truck heavily and struck it　43　meters away.

When Randolph Bruce, the driver was　44　out of the damaged truck, he was　45　hurt just　46　the young woman had foretold on the phone. As he was taken to the　47　in time, he was saved at last.

Later the policemen did　48　they could to find the woman who had telephoned them, but　49　.

It is　50　that a prophecy（预言）should coincide（巧合）with the fact so exactly.