Question

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? campfires left unattended can have significant consequences, such as forest fires. there are three reasons why fire is important to the development of mankind: warmth, protection, and cooking. one of the three elements that are required for fire to burn is oxygen. flames are the part of a fire that can be seen, and depending on the material being burned, they can be different colors.

Explanation:

The task is to write about the chemical process of fire. The first option is about consequences of unattended campfires, the second is about the importance of fire to mankind, and the fourth is about the appearance of flames. Only the third option, which mentions oxygen as one of the elements required for fire to burn, relates to the chemical - process aspect of fire.

Answer:

One of the three elements that are required for fire to burn is oxygen.