Answer: b. Because the opportunity cost of the fourth unit of capital is the consumption goods that must be given up for this economy to move from three units of capital to four units of capital, but the opportunity cost of four units of capital is the amount of consumption goods that must be given up to go from zero units of capital to four units of capital.
Explanation:
The opportunity cost of the 4th unit of capital refers to how many units of consumption need to be given up for the economy to move from the third unit to the forth unit of capital. In other words, the economy needs to give up 4 more goods to move from the 3rd unit of capital to the fourth.
But if the Economy was to produce the entire 4 units of capital it would have to give up the entire 10 units of consumption in total.