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]: The most significant human-induced impact on Earth's atmosphere comes from the use of which energy resource?
(A) flowing water (B) fossil fuels (C) sunlight (D) winds
[EX A]: B

[EX Q]: Which characteristic of sound makes it possible for bats to fly in the dark without hitting any objects?
(A) refraction (B) reflection (C) conduction (D) amplification
[EX A]: B

[EX Q]: Which color of light is produced when all of the colors of visible light in the electromagnetic spectrum are combined?
(A) gray (B) white (C) black (D) brown
[EX A]:
B