Pain
All of us have felt pain. We have cut ourselves. We have been burned. Or we have had headaches. Some of us suffer pain rarely. (46)
Pain can take complete control of our body and mind, making it impossible to move and even to think. Yet we need pain. Without it, we would not know if we have hurt ourselves. It is our body’s warning system. (47)
Pain is the most common reason we go to a doctor. It is the most common reason we take medicines. Until recently, however, most doctors knew of only a few drugs that stopped some pains. (48) But new knowledge about the process of pain is helping them to control pain better.
Scientists have learned that the sense of pain is made up of both chemical and electrical signals. (49) Scientists also have learned that the nervous system sends two different kinds of pain messages to the brain: one very fast, the other slow.
The first message is the warning signal. It moves at a speed of 30 meters a second. In less than a second, the brain understands that part of the body is hurt and how badly it is injured. (50) It tells us not to use the injured part until it heals.
A. And others have painful attacks all the time.
B. These signals travel from nerve cells in the injured area, up the spinal cord (脊髓) to the brain, and back down again.
C. It tells us that we are injured and should do something about it.
D. They knew little about the process of pain itself.
E. The other message moves at a speed of only one meter a second.
F. And they send the second, slower message of pain to the brain.

A hundred years ago, life expectancy in developed countries was about 47; in the early 21st century, men in the United States and the United Kingdom can expect to live to about 74, women to about 80, and these (51) are rising all the time. What has brought (52) these changes When we look at the life (53) of peoplel00 years ago, we need to look at the greatest (54) of the time. In the early 20th century, there were the acute and often (55) infectious diseases such as smallpox. Many children died very young from these diseases and others, and the weak and elderly were always at risk.
In the (56) world these diseases are far (57) today, and in some cases have almost disappeared A number of (58) have led to this: improvements in sanitation and hygiene, the discovery and use of antibiotics, which (59) bacterial diseases much less dangerous, and vaccinations (60) common diseases. (61) , people’s general health has improved with improvements in our general environment: cleaner air, better means of preserving food, better and warmer housing, and better understanding of nutrition.
Genetically, we should all be able to live to about 85 but (62) people do live longer today, there are still some big killers around that are preventing us from consistently reaching that age. The problems that affect people today are the more chronic illnesses, such as heart disease and strokes, and those (63) by viruses, such as influenza and AIDS. Of course, cancer is a huge killer as well. In most cases these diseases affect (64) people, but there are worrying trends in the developed world with problems such as obesity (65) more heart disease and illnesses such as diabetes at younger ages.
The killers today can be classed as "lifestyle diseases", which means that it may be possible to halt their progress.

A. try out the Japanese method in certain areas
B. change the road signs across the country
C. replace straight, horizontal bars with chevrons
D. repeat the Japanese road patterns