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:
What happens to the water vapor in an air mass as it ascends?  
 (A) It freezes. (B) It condenses. (C) It vaporizes. (D) It polarizes.
answer:
B


question:
One of the main causes of acid rain is  
 (A) Waste from nuclear power plants (B) Spills from chemical manufacturing plants (C) Gases from burning fossil fuels (D) Gases from aerosol spray cans
answer:
C


question:
Biologists conduct investigations to learn about living organisms. Which method helps reduce bias during an investigation?  
 (A) developing a hypothesis after collecting data in the investigation (B) limiting the amount of background research before the investigation (C) designing an investigation with repeated trials during the investigation (D) obtaining other opinions concerning what should happen during the investigation
answer:

C