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: carbon dioxide concentrations in the air have increased over the last decade dramatically, Fact2: CO 2 is carbon dioxide., Question: What has increased in the air dramatically over the last decade? (A) oil (B) sugar (C) coal (D) Cars (E) H2O (F) CO 2 (G) He (H) O2
A:
F