A、There are 30% of American women who develop cancer. B、Non-smoking women get lung cancer more easily than nonsmoking men. C、Tob

Experts say that each year more than one million people worldwide die of lung cancer. It is the leading cause of cancer death in both men and women. Last week, Dana Reeve died of lung cancer at the age of 44. Last August Dana Reeve announced that she had lung cancer. Smoking is linked to about 90 percent of cases. But Dana Reeve did not smoke. Researchers say this is true of up to 30 percent of American women who develop lung cancer.[30]In fact, experts say a higher rate of non-smoking women get the disease than non-smoking men.
    Studies have shown that men and women react differently to tobacco smoke. Scientists are not sure why. Some suggest that cells in women’s lungs might be more easily damaged by smoking. There could be genetic or environmental reasons.
    Experts say even people who do not smoke could still be considered "passive smokers" if they breathe other people’s tobacco. Derek Raghavan is director of the Cancer Center at the Cleveland Clinic in Ohio. He thinks second-hand smoke causes at least half the cases of lung cancer in non-smokers.
    A common sign of lung cancer is a cough that does not go away and gets worse over time. Other common signs include chest pain, coughing up blood, shortness of breath and repeated cases of pneumonia. By the time most people feel sick enough to see a doctor, the cancer has spread too far to be treated effectively.
29. What is the main cause of cancer death according to the experts?
30. Which of the following statements is true according to the experts?
31. What is the common sign of lung cancer?