What does the graph show the importance of clean air?

C. Most people will die from negative health effects associated with stroke as indoor dirty air builds up.

Explanation:

C is correct option because it shows the highest proportion of people's death caused by stroke. On the other options are not correct due to the following reasons:

A is incorrect because it says that people have a lower risk of dying from COPD. On the other hand, the graph shows that this is 3rd most abundant cause of deaths.

B is incorrect because deaths due to lung cancer are the lowest according to the graphical illustration.

D is incorrect because the proportion of developing acute lower respiratory infection and ischemic heart disease are not the same. Deaths due to ischemic heart disease are higher than the acute lower respiratory infection.

it would be c. xylem.