Which one is main idea? Number for answer and please i need this!
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 main idea of a paragraph states the primary point that the author wants to express and transmit to the reader. Generally, the main idea is announced in a single sentence and this sentence is usually located at the beginning of a paragraph. In the case of the paragraph provided, sentence 3) is the one that contains the main idea because it encompasses all the supporting details that are included in the rest of the sentences. In other words, sentences 1), 2), 4), 5), 6) and 7) provide supporting information for the main point stated in sentence 3).