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]: One type of animal hatches from an egg, breathes through gills when it is young, and mainly lives on land as an adult. Into which group is this animal classified?  
 (A) amphibians (B) birds (C) mammals (D) reptiles
[A]: A


[Q]: Which material is the best conductor of electricity?  
 (A) Wood (B) Metal (C) Stone (D) Plastic
[A]: B


[Q]: Which of the following is an example of a structural adaptation?  
 (A) a wolf's howl (B) an insect's coloring (C) a fish's fin (D) a squirrel storing acorns
[A]:
C