The object of the preposition is not the subject of a sentence and doesn't have to agree with the verb.
True or false

(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.”)

Constructed response paragraph: in the short story, the author describes her life during her “day away” but provides few details about her “normal” life. using information from the text, write a short story that describes events that precede the story above. as you detail the author’s daily routine before her “day away,” be sure your narrative establishes the story’s setting, first-person point of view, and primary conflict.

Correct sentence. when her brother boarded the ship bound for america, christina stood on the pier and tearfully waved goodbye.