i need to write essay between 200-500 word about all this information but i don't know how to start or to do it

Several different components/characteristics can be used to describe a market's producer structure (e.g. number of producers, marginal revenue, etc..).

What is the market component/characteristic that you feel best delineates the similarities and differences between Monopoly, Oligopoly, Monopolistic Competition and Pure Competition? Explain and defend your position.