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").
Input: Fact1: Blood pH may become unbalanced if the rate of breathing is too fast or too slow., Fact2: Aerobic activities are exercises that cause deep breathing and a fast heart rate., Question: what can cause blood pH to become unbalanced? (A) aerobic activities (B) h2o (C) the sun (D) Heavy rains (E) plasma (F) Dehydration (G) smoking cigarettes (H) cloudy and rainy weather
Output:
A