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 pull of gravity from Earth has the greatest effect on  
 (A) comets. (B) the Sun. (C) asteroids. (D) the Moon.
answer:
D


question:
A student placed a small chip of limestone into a hydrochloric acid solution, and carbon dioxide gas was released. The carbon dioxide provided evidence that   
 (A) only a physical change occurred. (B) a chemical change occurred. (C) only a loss of mass occurred. (D) the formation of an element occurred.
answer:
B


question:
Plants in a forest need to obtain nutrients from the soil to survive. How do most of the nutrients get back in the soil once the forest plants have used them for growth?  
 (A) Organic matter recycles from dead organisms. (B) Commercial fertilizers are applied by humans. (C) Solar radiation reaches the ground surface. (D) Rainwater drips off of living organisms.
answer:

A