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: a cactus stem is used for storing water, Fact2: Water consists of H2O, etc., Question: A cactus stem stores what? (A) RNA (B) h2o (C) rain (D) h1n1 (E) co2 (F) H20 (G) O2 (H) copper
A:
B