Which word is correctly used in the sentence?

my uncle will what i need.

by
buy

How does the poem's mood and tone change in each of these stages of “o captain! my captain! ” by walt whitman? (i need an answer asap )

(1) fire extended humans’ geographical boundaries by allowing them to travel into regions that were previously too cold to explore. (2) it also kept predators away, allowing early humans to sleep securely. (3) fire, in fact, has been a significant factor in human development and progress in many ways. (4) other obvious benefits of fire are its uses in cooking and in hunting. (5) probably even more important, however, is that learning to control fire allowed people to change the very rhythm of their lives. (6) before fire, the human daily cycle coincided with the rising and setting of the sun. (7) with fire, though, humans gained time to think and talk about the day’s events and to prepare strategies for coping with tomorrow. the sentence that expresses the main idea is: (type the number of the sentence. then click “go.”)

3. what is the purpose of a lead sentence or paragraph? to display your most convincing reasons and arguments to you revise the overall structure of your work to interest readers and introduce your writing style to add details and elaborate on your ideas