Definition: 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").
Input: Fact1: Fertilization occurs when a sperm and an egg fuse to form a diploid zygote., Fact2: Sexual reproduction requires formation of gametes, followed by fertilization., Question: What involves a sperm and egg fusing to form a diploid zygote? (A) Leptospirosis (B) produce offspring (C) allow growth (D) sexual reproduction (E) metabolic reaction (F) peachleaf willow (G) rapid expansion (H) Plant reproduction
Output:
D