Which sentence uses a comma correctly to set off an introductory phrase? O A. For example, I always turn in my homework on time and study for tests. O B. "Leave me alone!" he said, slamming the door. O C. To begin, with my aunt is making me babysit my cousins that day. O D. My best subjects are, math, music and spelling. don't get this wrong only answe if you know the right answer

(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.”)