Final answer:
A decrease in the price of gasoline will increase its demand, as lower prices make a product more attractive, leading to a higher quantity demanded. The correct option is B.
Step-by-step explanation:
The introduction of factors that encourage the use of gasoline will increase its demand. Of the options given, a decrease in the price of gasoline would most likely increase the demand for gasoline. This is because lower prices typically make a product more attractive to consumers, leading to a higher quantity demanded.
Conversely, an increase in electric vehicle sales, the introduction of more fuel-efficient engines, and the expansion of public transportation would all likely decrease the demand for gasoline as they provide alternatives or reduce consumption.