The demand for plums is unit elastic if __ A. my demand for plums increases when the price of apples falls B. a 5 percent rise in the price of plums results in a 5 percent decrease in the quantity of plums demanded C. any increase in the price of plums results in a 1 percent decrease in the quantity of plums demanded D. the price of plums does not change after a drought

The correct answer is B. a 5 percent rise in the price of plums results in a 5 percent decrease in the quantity of plums demanded.<br /><br />Unit elastic demand refers to a situation where the percentage change in quantity demanded is exactly equal to the percentage change in price. In other words, the price elasticity of demand is equal to 1.<br /><br />In the given options, option B describes a scenario where a 5 percent rise in the price of plums results in a 5 percent decrease in the quantity of plums demanded. This indicates that the percentage change in quantity demanded is equal to the percentage change in price, which is the definition of unit elastic demand.<br /><br />The other options do not accurately describe unit elastic demand. Option A is related to the substitution effect between plums and apples, option C does not provide enough information about the percentage changes, and option D is unrelated to the concept of unit elastic demand.