单项选择题
A．offer advice on how to give up smoking B．explain the influence of cigarette smoking on health C．list the factors that can cause cancer D．compare the opinions on the effect of smoking
A．More and more research workers believe the effect of cigarette smoking on health. B．Filters and low tar tobacco can not get rid of the danger. C．Cigarette smoking has a greater effect on health than cigar or pipe smoking. D．All forms of tobacco smoking affects life expectancy and health.
A．so B．or C．but D．and