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.

Example Input: A student notices a paw print while walking in a park. The paw print could be considered a fossil if the print was in ___.  
 (A) rock (B) topsoil (C) thick mud (D) loose sand
Example Output: A

Example Input: Which of these technologies helps a power company use renewable energy for the production of electricity?  
 (A) hydroelectric power (B) nuclear power plants (C) natural gas generators (D) coal-fired power plants
Example Output: A

Example Input: The layered mixture of gases surrounding Earth is called the  
 (A) atmosphere (B) hydrosphere (C) lithosphere (D) hemisphere
Example Output:
A