Pat's total utility after eating 99 Reese's Peanut Butter Cups was greater than his total utility after eating 100 Reese's Peanut Butter Cups. Therefore, Pat's marginal utility from the 100th peanut butter cup was:

A. positive, but less than one.
B. zero.
C. positive, but less than his marginal utility for the 99th peanut butter cup.
D. negative.

Answer: D