Vinny Consumes Tacos and Chicken Wings

Multiple Choice

Vinny consumes tacos and chicken wings.To keep his utility constant, he must consume more tacos if he consumes fewer chicken wings.This means that

A) Vinny's indifference curve for tacos and chicken wings must have a negative slope.
B) the prices Vinny pays for tacos and chicken wings are always the same.
C) Vinny's marginal utility from each good must be constant along his convex indifference curves for tacos and chicken wings.
D) Vinny's marginal rate of substitution must be constant along his indifference curves for tacos and chicken wings.