You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Ex Input:
Campers shouted toward a canyon wall. What characteristic of sound best explains why the campers heard an echo?  
 (A) Sound waves traveled slowly down the canyon. (B) Sound waves were absorbed by the canyon wall. (C) Sound waves reflected off the canyon wall. (D) Sound waves were refracted around the canyon.

Ex Output:
C


Ex Input:
What determines how long the Moon takes to complete one cycle of phases?  
 (A) the period of rotation of the Moon around its axis (B) the period of revolution of the Moon around Earth (C) the period of rotation of Earth around its axis (D) the period of revolution of Earth around the Sun

Ex Output:
B


Ex Input:
During the year, the angle at which the path of the Sun appears in the sky varies. In the Northern Hemisphere, the path of the Sun appears higher on the horizon during the summer and lower on the horizon during the winter. Which factor most contributes to the variation in the path of the Sun across the sky?  
 (A) the rotation of Earth (B) the tilted axis of Earth (C) the flattening of Earth at the poles (D) the elliptical shape of the orbit of Earth

Ex Output:

B