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.

Which of the following statements best explains how the decomposition of plant and animal matter helps to form rich soils?  
 (A) Decomposition adds silt to soil. (B) Decomposition adds water to soil. (C) Decomposition adds oxygen to soil. (D) Decomposition adds nutrients to soil.
D

Some birds fly south in the fall and return in the spring. This is an example of  
 (A) migration (B) camouflage (C) hibernation (D) growth
A

A rubber band will make a sound when it is  
 (A) vibrated. (B) stretched. (C) cut into pieces. (D) shot across a room.

A