I have attached the question that I need help with

A) If the researcher wants to see whether locating in different regions, namely, East Asia, Africa, and Latin America, affects the revenue incomes of countries in different regions, he can create dummy variables in the regression model. Which of the following can be a right way of doing so? O A. R1 = 0, if East Asia, and 1, otherwise; R2 = 1, if Africa, and 0 otherwise. O B. R1 = 1, if East Asia, and 0, otherwise; R2 = 1, if Africa, and 0 otherwise. O C. R1 = 1, if East Asia, and 0, otherwise; R2 = 1, if Africa, and 0 otherwise; R3 = 1, if Latin America, and 0 otherwise. O D. R = 1, if East Asia; = 2, if Africa, and = 3, if Latin America. B) Followed from last question, which region is the base case? O A. East Asia O B. there is no base case. O C. Africa O D. Latin America