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: a greenhouse is used to protect plants by keeping them warm, Fact2: Energy from the sun keeps the earth warm, enables plants to grow., Question: Greenhouses are used to what, using the energy from the sun? (A) heat skin (B) evaporation (C) protect plants (D) cool air (E) spread flower seeds (F) important habitats (G) food and shelter (H) reserve water
C