Which of the following best describes a carbohydrate?
a) carbohydrates are composed of amino acid monomers and are involved in cell signaling, cell transport, immune responses, and the cell cycle.
b) carbohydrates always consist of a five-carbon sugar, a nitrogenous base, and one or more phosphate groups and are used to store genetic information.
c) carbohydrates are organic macromolecules that are made up of carbon, hydrogen, and oxygen atoms and are used for energy storage or as structural molecules.
d) carbohydrates are organic macromolecules that are insoluble in water and have the ability to store energy for extended periods of time.