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.

[EX Q]: Which of these is a nonliving part of a forest?  
 (A) Tree (B) Soil (C) Worm (D) Mushroom
[EX A]: B

[EX Q]: On a cold, cloudy day, the local weather forecaster predicts that a high-pressure system will be moving into the area in the next 24 hours. Which weather conditions will this system most likely bring to the area?  
 (A) stormy (B) sunny (C) snowy (D) hot
[EX A]: B

[EX Q]: Lea is investigating how phosphates affect oxygen levels in pond water. For part of the investigation, she uses pond water that contains no phosphates. The pond water without phosphates would be what part of the investigation?  
 (A) conclusion (B) hypothesis (C) control group (D) experimental group
[EX A]:
C