Answer:
1. Is linked to heart disease
Step-by-step explanation:
We automatically rule out numbers 3 and 4 because smoking tobacco actually INCREASES heart rate and weakens the respiratory system. Also, we are talking about the circulatory system, so we automatically know it has something to do with the heart. There is definitely a link to heart disease and this is a lot more devastating than red blood cells. So I'd go with 1, unless your teacher taught you otherwise.