The one that presents a main idea is number (3) "Fire, in fact, has been a significant factor in human development and progress in many ways".
<u>The main idea of a paragraph states the primary point that the author wants to express and transmit to the reader</u>. 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,<u> 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</u>. In other words, sentences 1), 2), 4), 5), 6) and 7) provide supporting information for the main point stated in sentence 3).
