Explanation

Marginal utility is the change in total utility from consuming one more unit. When total utility is at its maximum, the marginal utility of the last unit is zero; when total utility is falling, marginal utility is negative; and when total utility is rising, marginal utility is positive. At the point of maximum total utility, marginal utility is zero while average utility is positive, so the two are not equal to each other. Statements A, B and C are correct descriptions. Hence option D is the incorrect statement.