The flow is like the fluency in an essay, so it's the arrangements and transition words to allow it to be told smoothly.
Answer:<span>b. the use of transition words between supporting paragraphs</span>
I only see 3 excerpts.....those I can see would be as follows:
1) Society and class
2) humankind and nature
3) evolution
Don't know why the other 2 excerpts don't show up (for me)
I think the answer is Protect the Earth
Ti could be a reference to a life impacting experience of just a reference to the past.