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
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Q: Which energy source is nonrenewable?  
 (A) sunlight (B) biomass (C) wind (D) fossil fuel

A: D
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Q: In which of the following taxonomic groups would organisms have the least number of similarities?  
 (A) kingdom (B) class (C) family (D) genus

A:
A
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