口语话题

【#第一文档网# 导语】以下是®第一文档网的小编为您整理的《口语话题》，欢迎阅读！

8. Please describe three waves of immigration in the USA. (e.g. where and why)

A: We will talk briefly about immigration, the history of immigration to the U.S., To immigrate means to move from one country to another. It is a permanent move. By contrast, you don`t immigrate there; you move there temporarily, because you plane to return to your country.

B: So to immigrate means to move to another country to live there indefinitely. Immigration happens all over the world. Most people do it to improve their economic or social situation.

A: Let`s start with the colonial period, the first wave of immigrant in the seventeenth century. Most immigrants were from Western Europe. Life was difficult, and some people did not survive, but in smaller numbers.

B: I should also point out that about 20 percent of the population at this time was African American. However, most weren`t immigrants; they were brought from Africa as slaves.

A: Well, the country was growing fast, some thought too fast. So in the1790s, laws were passed to control immigration for the first time. The second big wave of immigration happened between 1840 and 1920. During this wave, about 37 million people came to the U.S.

B: The industrial revolution had begun in Europe, causing a big shift from farming to factory jobs they knew. About 80 percent of these second wave immigrants were from all over Europe. During this second wave, Chinese workers also came to the U.S., mostly as contract workers.

A: About 9 million people entered the U.S. between 1900 and 1910.

B: As a result, the U.S. government decided that it needed to limit the number of immigrants. This led to a series of new laws.

A:Now let`s look at the third wave; the period from 1965 to the present time. In 1965, the quota system was abolished. Instead, a limit of 290000 was set on the total number of people who could enter each year.

B: During the 1970s and 1980s, about 80 percent of the immigrants were from Latin America and Asia, and only 20 percent were from Europe and elsewhere.

A: So, if you compare the second and third waves, you see that in the second wave it was mostly Europeans, and in the third wave it was mostly Latin Americans and Asians.

B: Again, economic opportunity was the main reason people immigrated. Incent years, many people in the U.S. have come to realize that the country`s greatest strength is the diversity of its people.


10. DNA testing has been widely used in the medical and judicial

fields. Please use examples to illustrate uses of DNA testing.

A: let`s consider DNA testing. One important use of DNA testing is testing identity, which is also called DNA fingerprinting. Here`s how a DNA fingerprint is done. Scientists take a small sample of someone`s hair or skin, which contain DNA.

B: I know, next, they treat the sample with chemicals and make a film, like a small photograph. On this film there is a visible pattern of black bars. This pattern of black bars is unique for each person.

A: So, a DNA sample from your hair identifies you, it`s like your fingerprint; it identifies you and you only.

A: I want to look at two applications, or uses, of DNA testing. First, how it can be used by doctors, and second, how it can be used by the police. Within healthcare, one important use is to identify potential for health problems. Researchers have found some genes linked to specific diseases.

B: For example, Huntington`s disease is linked to a defect in chromosome 4, and Alzheimer`s disease is linked to a defect in chromosome 19. A genetic link means that doctors know that if someone has defects in these genes, they`re more likely to get these health problems; their potential is increased.

A: After doctors perform DNA testing, they can then decide the best way to use the information. For example, they may give medication to prevent a disease from ever staring. Genetic testing can also be used to decide which medicine.

B: To me , this is very exciting and promising. There are tiny differences can affect which patients will be helped by a drug, and who may be harmed by it. This is, uh, a tremendous advantage. It saves lives and money.

A: Let`s look at how DNA testing is used by police. The police can use DNA fingerprints to identify and trace criminals. All they need is a small amount, or trace, of blood or hair from the crime scene.

B: If the DNA samples from the crime scene and the suspect match, the results, at least in the United States, can be used to help put someone in prison. In much the same way, DNA testing can be used to help innocent people in prison.

A: Now DNA testing has other possibilities that we won`t discuss today. But in any case, many people think about the negative uses of testing---the fear that it will be used against people or to create “perfect” habies. Others think about police being able to trace criminals and possible advances in healthcare.

B: But, another way to think about it is that it tells us more about who we are, and that`s the goal of biology---to understand nature.

本文来源：https://www.dy1993.cn/lz7.html