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: Courtship is behavior that is intended to attract a mate., Fact2: For example, female birds secrete estrogen in response to the courtship of their male mates., Question: What do birds secrete to attract a mate? (A) Energy. (B) Energy (C) fur and fat (D) seeds (E) oxygen (F) pollen (G) Estrogen (H) acetic acid
G