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:
In 1971, the bones of an extinct flying dinosaur were discovered. This kind of discovery helps everyone learn more about  
 (A) impact of humans on Earth. (B) effect of gravity on animals. (C) history of animal species on Earth. (D) likelihood that dinosaurs will reappear.
answer:
C


question:
The most common way humans contribute to the extinction of organisms is by  
 (A) rotation of crops. (B) use of fertilizers. (C) destruction of habitat. (D) introduction of competing species.
answer:

C