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]: Plants growing in a pond release a gas that fish need to survive. Which gas do the plants release that fish use?  
 (A) helium (B) hydrogen (C) nitrogen (D) oxygen
[A]: D


[Q]: What is the downward movement of water through pores and other spaces in soil due to the force of gravity?  
 (A) percolation (B) evaporation (C) precipitation (D) condensation
[A]: A


[Q]: Which description is an example of camouflage?  
 (A) plant leaves closing up when touched (B) butterflies migrating south for the winter (C) green insects sitting on green leaves (D) earthworms moving through soil
[A]:
C