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:
What are produced in both the male and female reproductive systems in humans?  
 (A) sperm (B) nutrients (C) fertilized eggs (D) sex cells

Ex Output:
D


Ex Input:
A meteoroid becomes a meteorite when it  
 (A) impacts the surface of a planet. (B) encounters the atmosphere of a planet. (C) makes a complete orbit around a planet. (D) starts to burn up in the atmosphere of a planet.

Ex Output:
A


Ex Input:
An ice cube melts on a hot summer day because the energy of the particles   
 (A) decreases over a period of time and is lost. (B) increases and the particles move apart. (C) causes the particles to move closer together. (D) is converted into potential energy.

Ex Output:

B