Which lifestyle choice can best reduce the risk of cardiovascular disease? a. avoiding exposure to uv light b. keeping your hands clean c. avoiding cigarette smoke d. keeping your vaccinations up to date

Cardiovascular system has to do with the heart, so anything to reduce the risk of that system (including the heart, bloodstream etc.) would be the answer for you. So just using Process of elimination:

A) Has to do with external exposure. No
B) Keeping hands clean No
C) Avoiding cigarette smoke Yes
D) Keeping your vaccinations up to date No

So your answer is C.