Detailed Instructions: In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Q: Fact1: Population density is the average number of individuals per unit of area or volume., Fact2: Economy is affected by population size and density., Question: What is affected by the average number of individuals per unit of area or volume? (A) goats (B) economy (C) cows (D) animals (E) vegetation (F) mammals (G) bushes (H) wind
A:
B