Given the task definition and input, reply with output. 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: Testosterone stimulates the reproductive organs to develop into male organs., Fact2: Male mammals have a tube-like organ called the 'penis'., Question: What causes the penis to develop? (A) Creatine (B) Energy (C) Estrogen (D) Testicles (E) matter vibrating (F) Testosterone (G) movement (H) It expands
F