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| Scientists have learned a great deal
about the kinds of food people need. They say that there are several kinds of
food that people should eat every day. What are these classes of food They are
1) green vegetables of all kinds, such as string beans, peas, lettuces, and
cabbages; 2) fruit, such as apples, peaches and bananas; 3) other vegetables,
examples of these are beets, onions, carrots, tomatoes and so on; 4) meat of all
kinds, fish and eggs; 5) milk and food made from milk, such as butter, cheese
and ice-cream; 6) bread or cereal. Rice is also in this class of food.
People in different countries and different areas of the world eat
different kinds of things. Scientists say that none of these differences are
really important. It doesn’t matter whether food is eaten raw or cooked, canned,
or frozen. It doesn’t matter if a person eats dinner at four o’clock in the
afternoon or at eleven o’clock at night. The important thing, they say, is that
every day a person should eat something from each of these kinds of
food. There are two problems, then, in feeding the
ever-increasing number of people on earth. The first is to find some ways to
feed the world population sd that no one is hungry. The second is to make sure
that people everywhere have the right kinds of food to make them grow to be
strong and healthy. |
What is important in eating, according to the scientists
A. Eat one’s meals at regular intervals.
B. Eat raw or cooked food, but not canned or frozen food.
C. Eat a variety of necessary foods.
D. Eat vegetables and fruits more than meat and cereal.
[简答题] Scientists have learned more about the way cancer spreads from one place in the body to another. Once it spreads, it gets more difficult to treat. Cancer is a disease of uncontrolled cell growth. Traditional thinking is that cells simply break off the main cancer, travel through the blood and grow in other organs.
But the new findings suggest there is more to this process. Researchers found that cells from the main tumor send out messengers. These prepare the new organ for a secondary tumor (瘤). It works this way. The primary tumor releases proteins called growth factors into the blood. They signal cells at the target organ to produce a sticky protein, called fibronectin. It attaches to the surface of bone marrow (骨髓) cells. The result is a kind of landing area for cancer to arrive and grow into a secondary tumor.
The bone marrow cells help make vessels for blood to pass through and feed the cancer cells. The researchers believe that without the bone marrow cells, the tum
