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").

[EX Q]: Fact1: Air pollution harms the respiratory and circulatory systems., Fact2: Cars are a significant source of air pollution., Question: What harms the respiratory and circulatory systems? (A) oil (B) rain (C) sulfur (D) cars (E) tires (F) coal (G) tar (H) bicycles
[EX A]: D

[EX Q]: Fact1: Antigens are molecules that the immune system recognizes as foreign to the body., Fact2: Children are born with an immature immune, or defense, system., Question: What are molecules that the defense system recognizes as foreign to the body? (A) Allergies (B) lungs (C) antigens (D) bacteria (E) parasites (F) atoms (G) red blood cells (H) acetic acid
[EX A]: C

[EX Q]: Fact1: knowledge of the stars can be used to navigate, Fact2: Star Star Generally speaking, the star is a symbol of hope and guidance in the midst of uncertainty., Question: How can we overcome uncertainty when lost? (A) feedback (B) Sleep (C) Navigate (D) vision (E) lamphreys (F) Wander (G) Pace (H) movement
[EX A]:
C