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: Migration is a type of movement that changes population size., Fact2: Movement is thought in motion., Question: migration changes population size via what? (A) wind (B) forces (C) abrasion (D) motion (E) distance (F) vehicles (G) Movement (H) speed
A:
D