You have been asked to write an essay about the chemical process of fire. Which of these is the most effective topic sentence for a paragraph in this essay? A) One of the three elements that are required for fire to burn is oxygen. B) Flames are the part of a fire that can be seen, and depending on the material being burned, they can be different colors. C) There are three reasons why fire is important to the development of mankind: warmth, protection, and cooking. D) Campfires left unattended can have significant consequences, such as forest fires.​