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:
Which tool is best used to collect information about the weather?  
 (A) ruler (B) stopwatch (C) thermometer (D) collecting net

Ex Output:
C


Ex Input:
Two atoms of oxygen combine to form pure oxygen gas. What is the electrical charge of the O_{2} molecules?  
 (A) positive (B) negative (C) neutral (D) variable

Ex Output:
C


Ex Input:
The rate at which a wave passes through a medium is known as its  
 (A) speed. (B) amplitude. (C) acceleration. (D) wavelength.

Ex Output:

A