Average revenue can be represented in a table or as a curve. For a perfectly competitive firm, the average revenue curve is a horizontal, or perfectly elastic, line. For a monopoly, oligopoly, or monopolistically competitive firm, the average revenue curve is negatively sloped.
Carbon is the main constituent of all living cells. It has chemical properties that make it the most important biological element. For instance, it forms strong chemical bonds and can form single bonds with up to four other atoms. It can bond to itself. It can also form double and triple bonds. Carbon is one of the only elements, because of its bonding properties, that can create long chain-shaped molecules or ring shaped molecules.
Of the 92 natural elements, 25 are essential for life. Of these, there are six main elements that are the fundamental building blocks of life. They are, in order of least to most common: sulfur, phosphorous, oxygen, nitrogen, carbon, and hydrogen. An easy way to remember this is SPONCH-a nice mnemonic.