文档介绍：阅读理解:
第十八篇Exercise Can Replace Insulin for Elderly Diabetics
第十九篇Prolonging Human Life
第二十四篇Sleep Lets Brain File Memories
第二十六篇Obesity: the Scourge of the Western World 
第二十八篇Diseases of Agricultural Plants
第三十篇Silent and Deadly
完型填空:
第九篇The Case of the Disappearing Fingerprints
第十篇Hospital Mistreatment
第六篇Once-daily Pill Could Simplify HIV1 Treatment
第十九篇Prolonging Human Life
Prolonging human life has increased the size of the human population. Many people alive today would have died of childhood diseases if they had been born 100 years ago. Because more people live longer, there are more people around at any given time. In fact, it is a decrease in death rates, not an increase in birthrates, that has led to the population explosion.
Prolonging human life has also increased the dependency load. In all societies, people who are disabled or too young or too old to work are dependent on the rest of society to provide for them. In hunting and gathering cultures, old people who could not keep up might be left behind to die. In times of famine, infants might be allowed to die because they could not survive if their parents starved, whereas if the parents survived they could have another child. In most contemporary societies, people feel a moral obligation to keep people alive whether they can work or not. We have a great many people today who live past the age at which they want to work or are able to work; we also have rules which require people to retire at a certain age. Unless these people were able to save money for their retirement, somebody else must support them. In the United States many retired people live on social security checks which are so little that they must live in near poverty. Older people have more illness than young or middle-aged people; unless they have wealth or private or government insurance, they must often "go on welfare" if they have a serious illness.
When older people e senile or too weak and ill to care for themselves,