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: sonar is used to find the location of an object, Fact2: Sonar bounces sound waves off the bottom of the ocean., Question: What can be bounced off the ocean floor to located objects? (A) soundwaves (B) rubber balls (C) submarines (D) whale bones (E) electricity (F) rays or beams (G) light (H) satellites
A