2. 外语
  3. To preserve food, the growth of bacteria (细菌) must be controlled. Water, warmth, and food are all needed for bacteria to become

To preserve food, the growth of bacteria (细菌) must be controlled. Water, warmth, and food are all needed for bacteria to become

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问题     To preserve food, the growth of bacteria (细菌) must be controlled. Water, warmth, and food are all needed for bacteria to become strong and healthy. Some kinds of bacteria need air, but other kinds grow only when air is absent. Extremes of temperature, either hot or cold, can kill bacteria.
  Before electric ice boxes were invented, freezing and cooling were limited by the cold climate. In warmer regions, food was cooled by putting it in the shade, in cold water from the well, or in pits in the ground.
    Cooking will usually kill bacteria if the temperature is high enough and long enough. Certain methods of cooking remove water, and this aids in preserving food. Drying is the oldest and most common method of preserving food. Food can be dried by the sun, by heat or by combination of the two.
    Salt was used by many hunting people. When people began to cat vegetables, salt be came a needed part of their life. Salt helps to preserve food because it slows or stops bacteria growth. Other chemicals besides salt are used in preserving foot. Some people oppose the use of chemicals in food. They say that these chemicals may harm people if the chemicals can harm bacteria.
Many people are against the use of chemicals to preserve food because      .
选项 A、chemicals are not necessary for preserving food
B、a small quantity of bacteria in food is good to the body
C、those chemicals that kill bacteria may not be good to people
D、there are other better ways to preserve food
答案C
解析 根据题干中的关键词against the use of chemicals定位到文章末段末尾两句Some people oppose the use of chemicals in food. They say that these chemicals may harm people if the chemicals can harm bacteria、可知，许多人反对使用化学物质来保存食物。他们认为化学物质既然能杀死细菌，也就有可能对人体有害。由此可知人们反对使用化学物质来保存食物的原因是these chemicals may harm people.答案选C.
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