Question

Can somebody paraphrase this for me?

Smoking causes the majority of lung cancers — both in smokers and in people exposed to secondhand smoke. But lung cancer also occurs in people who never smoked and in those who never had prolonged exposure to secondhand smoke. In these cases, there may be no clear cause of lung cancer.

Answer 1

there is no clear cause of lung cancer but smoking and being exposed to second hand smoke greatly increases your chance.