If a Production Possibility Frontier Is Drawn Concave to the Origin

Multiple Choice

If a production possibility frontier 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 upward along the PPF reflects:

A) an increasing opportunity cost of T-shirts.
B) an increasing opportunity cost of both shoes and T-shirts.
C) a decreasing opportunity cost of T-shirts.
D) a decreasing opportunity cost of both shoes and T-shirts.