The largest chicken meat producer in the United States says it will stop giving its birds antibiotics（抗生素） that doctors use to treat humans. Tyson Foods made the announcement on April 28. It said it plans to complete the change by 2017.

Health experts say overuse of the medicines is part of the reason that more bacteria are becoming resistant（耐药性） to them.

Farmers have fed livestock（家畜） small amounts of antibiotics for many years. The drugs help the animals grow faster and prevent the spread of sickness among farm animals that live close together.

But bacteria（细菌） living in and on the animals develop and become immune to the drugs. In other words, the antibiotics no longer have any effect. These drug-resistant bacteria then enter the bodies of people who eat the birds or livestock. Then, diseases in humans become more costly and difficult to treat. Sometimes, treatment does not work at all.

Donnie Smith is the president of Tyson Foods. He says the company has already begun reducing its use of antibiotics.

"As a result of our efforts, only a very small percentage of our chicken flocks（鸡群） receive human antibiotics today."

While the use of antibiotics in birds and livestock is decreasing in the U.S. and Europe, it is expected to increase in the developing world. There is a growing demand for meat there. Livestock producers in those countries are using methods that require antibiotics to keep animals healthy.

Ramanan Laxminarayan is the director of the Center for Disease Dynamics, Economics and Policy（美国疾病动态、经济和政策中心的主任）. He says Tyson's announcement shows food producers can continue to operate without using the drugs.

Mr. Laxminarayan says if producers provide cleaner living conditions and better nutrition for their animals, they will not need to give them antibiotics. But he says the buying public must pressure farmers to stop using the drugs.

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1.Antibiotics used to treat humans___________to chickens by food producer Tyson Foods.

A are not given

B are stopped being given

C haven’t been used

D are still used

解析：选D。D。推理判断题。泰森食品公司宣布的是将停止对家禽使用抗生素，而完全改变这一状态还要到2017年，所以可推知，现在还在使用抗生素。

2.Why do farmers feed antibiotics to their chickens?

A To prevent the spread of diseases.

B To prevent them from growing.

C To stop bacteria from becoming resistant.

D To help the bacteria to grow.

解析：选A。A。细节理解题。给家禽喂抗生素，目的主要有两个，一是长得快，二是防止疾病传播。

3.What might happen if people eat the chicken with drug-resistant bacteria?

A People become immune to the drugs.

B People don’t work with disease.

C Diseases in humans are hard to treat.

D Drugs become more expensive for people.

解析：选C。C。细节理解题。文章第4段告诉大家，这些具有耐药性的病毒进入人体，要治疗起来就更困难。

4.The underlined sentence implies that____________.

A people all over the world are trying to reduce the use of antibiotics

B the situation will become worse in poor countries

C the number of birds and livestock will decrease in developed countries

D the U.S. and the Europe hope to increase the use of antibiotics

解析：选B。B。句子理解题。这里的while引导的是让步状语从句，表示：虽然。即发展中国家使用却越来越多。

5.What does the underlined word “pressure” in the last paragraph mean?

A permit

B forbid

C encourage

D force

解析：选D。D。词义猜测题。前面说，虽然情况是越来越好，但公众还须对家禽饲养者施压，使他们完全放弃在饲养家禽时使用抗生素。