On a Diagram of a Production Possibilities Boundary,the Concept of Choice

Multiple Choice

On a diagram of a production possibilities boundary,the concept of choice is illustrated by the

A) negative slope of the boundary.
B) unattainable combinations outside the boundary.
C) need to select among the alternative attainable points along or inside the boundary.
D) the concave shape of the boundary.
E) the distance from the origin to the boundary.