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: Infancy is the period of most rapid growth after birth., Fact2: Infants are birth to one year., Question: The first year is the period of what? (A) communication (B) blossoms (C) rapid growth (D) Flowers (E) flower secretion (F) Prehistoric (G) Mesozoic (H) melanin content
C