Points on opposite sides of the PPC: one inside (attainable, inefficient) and one outside (unattainable).

Steps:

• The PPC curve separates inside points (attainable but inefficient) from outside points (unattainable without growth).
• Point K is outside the PPC, as it requires economic growth.
• Point M lies on the PPC, indicating efficient production.
• From the diagram, identify N inside the curve and R outside to find opposites.

Why C is correct:

• N (inside, attainable inefficiently) and R (outside, unattainable) lie on opposite sides of the PPC, per the curve's boundary definition.

Why the others are wrong:

• A: K and N are opposite only if N is inside, but diagram shows N inside while L may not pair oppositely with R.
• B: L and R could both be inside or on the same side, not guaranteed opposite.
• D: S is not mentioned or shown in the diagram.

Final answer: C