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:
A radio station broadcasting across a large area is experiencing thunderstorms. How will the radio waves from the station be affected?  
 (A) wavelength will be increased (B) amplitude will be unchanged (C) frequency will be distorted (D) speed will be decreased

Ex Output:
C


Ex Input:
A scientist combines oxygen and hydrogen to form water. This combination illustrates that water is  
 (A) an atom. (B) an element. (C) a mixture. (D) a compound.

Ex Output:
D


Ex Input:
The length of a year is determined by the amount of time it takes  
 (A) the Moon to revolve around Earth. (B) Earth to revolve around the Sun. (C) Earth to rotate on its axis. (D) the Sun to rotate on its axis.

Ex Output:

B