Production Possibility Curve is concave to the origin when two products substitute each other at a/an (MPSC Main paper-2, 2017)

✅Explanation: A Production Possibility Curve (PPC) is concave to the origin when there is an increasing opportunity cost. This means that as you produce more of one good, you have to give up increasing amounts of the other good. This occurs when resources are not perfectly adaptable between the production of the two goods.