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").

Fact1: Air pollution harms the respiratory and circulatory systems., Fact2: Nitrogen oxides cause air pollution., Question: Harm to the respiratory and circulatory systems can come from (A) Greenhouse gases (B) hydrocarbons (C) Sulfur dioxide (D) nitrogen oxides (E) burning coal (F) fossil fuels (G) emissions (H) Greenhouse gasses
D