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:
The burning of fossil fuels affects the atmosphere by
(A) adding more heat and carbon dioxide. (B) reducing the amount of necessary heat. (C) taking water vapor out of the atmosphere. (D) putting more oxygen in the atmosphere.
answer:
A

question:
Which property of proteins best allows them to perform an enormously diverse range of functions?
(A) their large, chemical-energy reserve (B) their large, stored-electric potential (C) the complexity of their folded structure (D) the wide variety of elements they include
answer:
C

question:
A research scientist writes a paper on the initial regrowth of a forest after a fire has damaged the entire ecosystem. Which title would be best for the paper?
(A) Primary Succession (B) Stable Communities (C) Climax Communities (D) Secondary Succession
answer:
D