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: After a star runs out of most of its hydrogen fuel, it becomes hotter and more luminous. What stage does this represent in the life cycle of a star?  
 (A) quasar (B) protostar (C) red giant (D) white dwarf
Example Output: C

Example Input: Many things can contribute to the development of a theory. A student made a list of some things that might help scientists develop a theory. Observations Calculations Conversations Publications From the student's list, which must be used in the development of every theory?  
 (A) Observations (B) Conversations (C) Publications and calculations (D) Calculations and conversations
Example Output: A

Example Input: The Florida Bog Frog (Lithobates okaloosae) inhabits shallow stream overflows in three counties in Florida. With such a small geographic habitat, any change in the frog's environment could cause drastic changes in the population. Which would most likely affect the frog population if acid rain changed the pH of the water?  
 (A) Prey insects would become inedible. (B) Tadpoles would be unable to survive. (C) Breeding sites would become unavailable. (D) Predators would choose another food source.
Example Output:
B