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.

Input: Consider Input: A scientist is searching for areas where new solar systems might form. What feature is the scientist looking for?  
 (A) a star similar to our Sun (B) a cloud of dust and gas (C) an oxygen-rich atmosphere (D) a gravitational acceleration of 9.8 m/sec2

Output: B


Input: Consider Input: As water cools to a temperature of zero degrees Celsius and forms ice, water molecules tend to  
 (A) move farther apart. (B) vibrate rapidly. (C) flow more randomly. (D) gradually expand.

Output: A


Input: Consider Input: Some students were on a tour exploring the inside of a cave. While the students were in the cave, they realized they heard an echo every time that they spoke. Which most likely caused the echo to occur?  
 (A) the accumulation of the sound waves (B) the diffraction of the sound waves (C) the refraction of the sound waves (D) the reflection of the sound waves


Output: D