听力原文： Long ago, people had no way of keeping food from spoiling. So they ate all they possibly could and hoped it wouldn't be too long before the next meal. Mealtime was any time they found food, so they were either stuffed or starved most of the time.
No one knows for sure how people first learned to preserve food. Maybe they accidentally left food in the sun and discovered that the dried food kept longer. Maybe they left food by the fire and found out that cooked food not only kept longer, but tasted better. Somehow someone learned that salt helps preserve meat, fish and even vegetables. For example, pickles are cucumbers that are preserved with salt. Through the years people have continued to learn new and better ways of preserving food from one growing season to another. Today millions of people work in jobs that have something to do with food preservation.
Suppose you were walking up and down the aisles of a modern supermarket. On the shelves you would find food preserved in many different ways. You would see canned tomatoes and peaches in glass jars. These foods were first sealed in airtight containers and then heated to high temperature. If there was a break in the seal, the food would soon spoil You would also see dried and powdered food on the shelves. You would see prunes and raisins. You would see powdered milk and powdered eggs. Some dried foods, such as onions and potatoes, can of course be kept for tong.
If you walked past the dairy counter, you would find many foods that have been treated to kill any harmful germs that might have been in them. Milk is a good example. It may be unsafe to drink ram milk, that is, milk just as it comes from the cow. If the milk is heated and then cooled, the harmful germs are killed. The man who discovered this way of treating milk was a Frenchman named Louis Pasteur. Milk so treated is called pasteurized milk and the process is called pasteurization.
In the supermarket you would also find many frozen foods, frozen fruits, vegetables, meat and fish. Because techniques for freezing food are being improved, more and more frozen foods are appearing on the market, and more and more people are buying them. Fruits and vegetables sold in the supermarket are often frozen as soon as they are picked. The sooner fruits and vegetables are frozen, the better freezing machines can be taken into fields where the food grows, so that little time is lost between picking and freezing.
Many Americans with large families now have their own freezers and freeze their own food. Because fruits and vegetables are cheaper when they are in season, a housewife often buys more than she can use in a few days or even in a week and then freezes the rest. Preparing food for the freezer is a fairly simple process. To prepare strawberries, for example, the housewife simply needs to clean them, put them on a tray in the freezer for a few hours, then put them in plastic bags. Bread, cakes, cooked and uncooked pies can also be kept in a freezer.
With the improvement in methods of food preservation, people no longer have to stuff one day and starve another. They can have a well-balanced diet all year round.
Questions:
16. Which of the following is NOT an early way to keep food from spoiling？
17.Which of the following statements is TRUE about milk？
18.How can peaches sold in a supermarket be preserved, according to this talk？
19.How do most American housewives deal with fruits and vegetables？
20.According to this talk, what is NOT needed when strawberries are stored in a freezer？
(36)

A. Pasteurizing the food.
B. Pickling the food.
Cooking the food.
Drying the food.