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: propulsion is used for flying by a spacecraft, Fact2: All rockets operate on the same basic principles of propulsion., Question: What can spacecraft use to fly? (A) liquids (B) satellites (C) rockets (D) hovercraft (E) missiles (F) jetpacks (G) air masses (H) Gravity
C