Answer:
c. An economy can produce at any point on or inside the production possibilities frontier, but not outside the frontier.
Explanation:
Production Possibility Frontier is graph representing product combinations, that an economy can produce with given resources & technology.
A fundamental assumption of PPF is that : Goods are fully efficiently utilised. So, PPF reflects full production potential of economy, with given resources & technology.
Therefore : An economy can produce on PPC ; under PPC ; but can't produce outside PPF