Which one of the following statements best explains why gases are not comercially sold by volume? a)Gas volume is neligible b)Gas volume is difficult to measure c)Gas volume depends on the type of gas d)Gases have comparitviely low densities e)Gas volume depends on temperature and pressure The question is asking why aren't they sold by volume. Because the volume of a gas could change due to pressure and temperature changes would be my answer. e). I may have just answered my own question.