Ineed with this question which group of words best the reader understand the meaning of the word cumulative in this sentence?

many people consider global warming, also called climate change, to stem directly from the cumulative impact of air, land, and water pollution, as well as other human activities.

many people consider global warming

also called climate change

air, land, and water pollution

to stem directly from

the purpose of the heading in the passage is to identify who is telling the story.

this excerpt is part of the book sugar changed the world (2010) written by marc aronson and marina budhos. as the book has been written by two people, the heading "marc" indicates that this specific excerpt is being narrated by aronson. in the fragment, marc describes his grandfather's story after hearing it from his cousin. however, there are other excerpts where budhos is the one that tells the story of her family.

aronson and budhos, who are husband and wife in real life, decided to write sugar changed the world when they found out how sugar, which had an important role in slavery and economy, changed their ancestors' lives.