Moving Between Two Points on a PPF, a Country Gains

Multiple Choice

Moving between two points on a PPF, a country gains 6 cars and forgoes 3 trucks. The opportunity cost of 1 car is

A) 1/2 of a truck.
B) 2 trucks.
C) 3 trucks.
D) 6 cars - 3 trucks.
E) 1 car.