One way to explain the convexity of isoquants is to say that
A) as labor increases and capital decreases, MPL rises while MPK falls.
B) as labor increases and capital decreases, MPL falls while MPK rises.
C) as labor increases and capital decreases, MPL and MPK both fall.
D) as labor increases and capital decreases, MPL and MPK both rise.
Answer: as labor increases and capital decreases, MPL falls while MPK rises.