Like the simple Ricardian model, the specific factors model () A. assumes an economy that produces two goods and that can allocate its labor supply between the two sectors. O B. distinguishes between mobile and specific factors. O C. has a production possibilities curve that reflects diminishing returns to labor. O D. allows for the existence of factors of production besides labor.According to the gravity model, a characteristic that tends to affect the probability of trade existing between any two countries is O A. their colonial-historical ties. O B. the average weight/value of their traded goods. O C. the distance between them. O D. the number of varieties produced on the average by their industries. O E. their cultural affinity