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]: While conducting an experiment on gravity, what will be needed to ensure the safety of students?  
 (A) quiet zones (B) drop zones (C) heavy objects (D) frictionless surfaces
[EX A]: B

[EX Q]: In Maryland, most bears have thick, dark fur. Which statement best explains how dark fur helps bears survive in the forests of Maryland?  
 (A) Dark fur is lightweight. (B) Dark fur scares enemies. (C) Dark fur helps bears hide. (D) Dark fur keeps bears cool.
[EX A]: C

[EX Q]: When a large oak tree is cut down in a forest, it leaves a gap in the forest canopy which allows smaller trees to quickly grow in the available sunlight. Which interaction is best represented among the smaller trees?  
 (A) parasitism (B) mutualism (C) competition (D) commensalism
[EX A]:
C