What health consequence of tobacco use does this video primarily address?

Causation can be proved by using an

Which statement is true about common childhood infectious disease? a. children should always be given antibiotics to treat an infectious illness. b. frequency of infectious illnesses usually increases as children grow older. c. having a minor infectious illness weakens a child's immune system. d. infectious illnesses are usually mild and require no medication.

per vehicle mile, motorcyclists are times more likely to die in a crash than passenger car occupants.