After the crops have been harvested, workers are needed to prepare them for use. Some fruits and vegetables are sold fresh, some are frozen, some are preserved in cans and jars. Some grains must be ground to make flour; others are cut up to be used for animal food.

    Cows, sheep, goats, pigs, chickens, turkeys, and other animals are raised to provide meat for the world’s daily diet. These animals must be fed healthful food. Then they must be killed and their meat must be prepared. Good butchers are important, because meat must be correctly cut.

Fish are caught in oceans, rivers, and lakes by people who work on large fishing boats. After the fish have been bought to the shore, some of them might be cleaned and sent to stores and markets in refrigerator trucks. Others are sent to places where they are preserved by drying, smoking, salting, or freezing. Some fish are put into cans.

    Fast transportation methods are important in supplying food to consumers. Most of our food is sent first to large central areas, and then to supermarkets, stores, schools, hotels, hospitals, restaurants, and other places where food is sold or served.

21.When people learned to grow plants and raise animals for food (     ), there were only about (    ).

  A. 1,000 years ago, 50,000,000 people             5,000 years ago, 10,000,000 people

  C. 10,000 years ago, 5,000,000 people             15,000 years ago, 500,000 people

22.Farming has now become big business. Huge areas of land are used to raise (     ).

  A. several kinds of crops                                B. two kinds of crops

  C. many kinds of crops                                  D. one kind of crop

23.Which of the following is NOT suggested in the text?

  A. producing better crops

B. improving the transportation of crops