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: Two identical books are on opposite ends of a table. Which of these would increase the gravitational force exerted between the two books?  
 (A) decrease the distance between the books (B) decrease the mass of the books (C) decrease the mass of the table (D) decrease the temperature in the room
Example Output: A

Example Input: Some kinds of fish live most of their lives in salt water but lay their eggs in freshwater. Their ability to survive in different environments is an example of  
 (A) adaptation (B) developmental stages (C) a habit (D) selective breeding
Example Output: A

Example Input: Which is the best plan to make the fossil fuel supply last longer?  
 (A) mine more coal (B) reduce car pollution (C) produce more gasoline (D) reduce electricity use
Example Output:
D