Which of the following statements is true about the relationship between demand curves and marginal utility? Question 6Answer a. Demand curves are downward sloping because marginal utility decreases as the quantity of goods consumed increases. b. Demand curves are upward sloping because marginal utility increases as the quantity of goods consumed increases. c. Demand curves are horizontal because marginal utility is constant as the quantity of goods consumed increases. d. Demand curves are vertical because marginal utility is zero at all levels of consumption