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: carbon dioxide concentrations in the air have increased over the last decade dramatically, Fact2: Carbon dioxide is the primary greenhouse gas., Question: What have increased over the last decade dramatically (A) gasoline concentrations (B) Warm air moving into cold air (C) Greenhouse gases (D) treehouse gas concentrations (E) movements in the earth's crust (F) concentrated orange juices (G) genetic diversity (H) greenhouse gas concentrations
H