Concept:Marginal utility is the change in total utility from consuming one extra unit.
Mathematically, it is the slope of the total utility curve.
Explanation:Total utility first rises as more units are consumed.
At the point where total utility reaches its maximum, the curve becomes flat.
A flat curve means the slope is zero.
Since marginal utility equals this slope, marginal utility becomes zero at maximum total utility.
So, when total utility is maximum, marginal utility is zero.
Answer:The correct option is B: The marginal utility is always zero whenever the total utility reaches the maximum.