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").

Fact1: Population density is the average number of individuals per unit of area or volume., Fact2: Population densities affect the balance of the environment., Question: The average number of individuals per unit of area affect the balance of . (A) gravity (B) the environment (C) energy (D) Earth orbiting the Sun (E) an organism's body (F) objects that have mass (G) competition (H) power
B