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.

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


[Q]: Overuse of soil for farming causes local disruptions of several Earth subsystems. Which of these is a part of the biogeochemical cycle that experiences the most severe local disruption?  
 (A) release of carbon into the atmosphere (B) release of oxygen into the atmosphere (C) cycling phosphorus into the soil (D) cycling hydrogen into the soil
[A]: C


[Q]: Which tools are needed to measure the effects of friction on a block of wood?  
 (A) meter stick, spring scale (B) balance, stopwatch (C) balance, meter stick (D) meter stick, stopwatch
[A]:
A