The potential for gains from the rearrangement of production among countnes is due to O A. scarcity. O B. differing opportunity costs. 0 C. absolute advantage. O D. tradeoffs. Unlike the simple Ricardian model, the specific factors model O A. has a production possibilities frontier that is a straight line. O B. does not distinguish between mobile and specific factors. O C. allows for the existence of factors of production besides labor. O D. assumes an economy that produces two goods and that can allocate its labor supply between the two sectors