[originaltext] (29)Cancer is the second leading cause of death after heart d

(29)Cancer is the second leading cause of death after heart disease.
    Death rates for both diseases are falling. But researchers say the rate for heart disease is falling faster. As a result, an American Cancer Society report shows that cancer now kills more Americans under the age of eighty-five than any other cause.
    Some cancers can be prevented or treated, especially if found early. Cancer is the name for a group of diseases. All involve the uncontrolled growth and spread of cells that are not normal. Cell growth and division are controlled by genes. (30) Some cancers are linked to family genetics. Pollution and chemicals can also raise a person’s risk of cancer.
    The report shows that in recent years, cancer rates in the United States have dropped about one percent per year. Lung, colon, breast and prostate cancer make up more than half of all the cases. For men, prostate cancer is the most common. For women, it is breast cancer. Rates of both have continued to increase, but more slowly than in the past.
    Smoking causes about one-third of all cancer deaths. Poor diet and a lack of exercise are blamed for another third in the United States.
    (31) The American Cancer Society says cancer deaths worldwide could increase nearly one hundred percent in the next twenty years. Yet most could be avoided. The report calls tobacco use "the number one cause of cancer and the number one cause of preventable death throughout the world. "
    Hepatitis and other infections will cause an estimated seventeen percent of new cancers worldwide this year. (32) Such cancers are especially common in developing countries, and many of these cases can also be prevented.
29．What is the first leading cause of death?
30.What can be learned about cancers from the passage?
31.What does the American Cancer Society say about cancer?
32.What do we learn about cancers in developing countries’?