The conclusion drawn above depends on which of the following assumptions? A. Consumers are usually unaware of variations in the quality of the gasoline they buy unless those variations are announced by the gasoline companies. B. When tankers make gasoline deliveries at Haibei's seaport, the storage tank on Haibei always receives the same quantity of gasoline as that in the preceding delivery. C. There is a wide variation in the prices at which the different brands of gasoline on Haibei are sold. D. If any gasoline company on Haibei alters the quality of its gasoline before sale, the other gasoline companies also use methods before sale that result in the same change in the quality of their gasoline . E. The gasoline storage tank on Haibei is large enough to meet the needs of all of Haibei's different gasoline companies.