Answer:
B) 2
Explanation:
Since Sam MacDonald's faces a linear production possibility frontier and can produce 200 pounds of cabbages or 100 pounds of potatoes, then he can produce 2 pounds of cabbage for every pound of potato produced (= 200 pounds / 100 pounds).
For example, if he needed to produce 10 pounds of potatoes, then his opportunity cost would be 20 pounds of cabbages.