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 of the following is the best example of potential energy?  
 (A) a fallen rock (B) a burning match (C) a liter of gasoline (D) a red-hot piece of iron

Ex Output:
C


Ex Input:
All of the planets in the solar system formed at about the same time from a large cloud of gas and dust. How is Earth different from other planets in the solar system?  
 (A) Earth has no natural satellites. (B) Earth's atmosphere is composed of gases. (C) Water is found in all three phases on Earth. (D) Volcanoes release liquid rock onto Earth's surface.

Ex Output:
C


Ex Input:
Which human organ system produces sperm or egg cells?  
 (A) digestive system (B) nervous system (C) respiratory system (D) reproductive system

Ex Output:

D