If a Production Possibility Frontier (PPF)is Drawn Concave to the Origin

Multiple Choice

If a production possibility frontier (PPF) is drawn concave to the origin with the quantity of shoes on the X-axis and the quantity of T-shirts on the Y-axis,a movement downward along the PPF reflects:

A) an increasing opportunity cost of producing T-shirts.
B) an increasing opportunity cost of producing shoes.
C) constant opportunity cost of producing T-shirts.
D) constant opportunity cost of producing shoes.