"The ban on smoking in designated public places can save a large number of people from the well-known effects of environmental tobacco smoke. Passive smoking seriously impairs respiratory health. The ban rightly seeks to protect non-smokers from its ill effects."
Throughout the passage the main talk is about "ban". Though options A and C are mentioned in the passage, the main meaning of the passage is given by option B -- "The ban on smoking in public places protects the non-smokers."
Correct Option: B.