The study describes smoking as the biggest cause to deadly diseases among grown-ups in industrial countries. So far most of the smoking deaths have happened on men, especially in developing countries.
A researcher at the World Health Organization says 70% of Chinese men smoke more than 15 cigarettes each day. In Latin America about 50% of the men are smokers. There also is a very large number of smokers in the former Soviet Union(苏联)and in the east Europe. And 25% of all smoking deaths worldwide are in those areas of the world. Scientists say smoking will kill 50% of the countries.
Smoking is known to cause lung cancer. It also can lead to cancer of the mouth and other parts of bodies. Smokers are more likely than non-smokers to suffer from heart disease.
Experts say that people reduce their chance of dying from smoking if they stop smoking completely. They say smokers who give up smoking can improve their health.
The main idea of this passage is that ______.

A. we must give up smoking
B. smoking causes lung caner
C. smoking does harm to health
D. men like smoking much more than women