Which is a public good? A. school building
B. road
C. college education
D. health care

When tobacco smokers fall sick, the whole society has to pay for this: they would be treated by the  heath system, which is financed by the contributions by the whole society, not only smokers. (this means that options  A) and D) are wrong.

Aditionally, the negative effects are experienced also by the family of smokers,

So the correct answer is C (by taking extra break, being less fit and falling sick)