instruction:
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.
question:
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.
answer:
A


question:
Large amounts of industrial gases are released into the atmosphere every day. What happens to those gases?  
 (A) They are broken down by ultraviolet light from the Sun. (B) They are converted into nitrogen and oxygen. (C) They rise through the atmosphere and go into outer space. (D) They remain in the atmosphere for long periods of time.
answer:
D


question:
How is the stratosphere different from the troposphere?  
 (A) The clouds in the stratosphere produce more rain. (B) The air in the stratosphere has a greater density. (C) The composition of the stratosphere lacks ozone. (D) The temperature of the stratosphere warms at higher altitude.
answer:

D