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.

[EX Q]: A star is a large astronomical body that  
 (A) reflects light. (B) condenses light. (C) emits light. (D) absorbs light.
[EX A]: C

[EX Q]: 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
[EX A]: A

[EX Q]: Pepsin is an enzyme that acts in the stomach for protein digestion. Which of these is most likely the main role of pepsin in this metabolic reaction?  
 (A) to speed up the rate of reaction (B) to reduce the loss of energy as heat (C) to control the direction of the reaction (D) to protect the reaction from other chemicals
[EX A]:
A