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 energy source is considered nonrenewable?  
 (A) moving water (B) fossil fuel (C) wind (D) biomass
B

How do most fish get the oxygen they need to survive?  
 (A) They take in water and break it down into hydrogen and oxygen. (B) Using their gills, they take in oxygen that is dissolved in water. (C) They get their oxygen from the food they eat. (D) They come to the surface every few minutes to breathe air into their lungs.
B

Toads lay their eggs in ponds. Tadpoles hatch from the eggs and eat the plants floating in the pond. Which resource is most important for toads to survive?  
 (A) grass (B) rocks (C) trees (D) water

D