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: When microorganisms deplete the oxygen in soil through respiration, the soil becomes  
 (A) humus. (B) anaerobic. (C) compost. (D) aerobic.
Example Output: B

Example Input: A hardware designer finds that the wiring in a circuit is releasing enough heat to make the circuit dangerously hot. Which change would best solve this problem?  
 (A) increasing the current in the circuit (B) placing rubber insulation on wires in the circuit (C) reversing the direction of current flow in the circuit (D) using circuit wires with a lower resistance
Example Output: D

Example Input: Every organism in an ecosystem receives energy from another source. Which of these organisms receives its energy directly from the Sun?  
 (A) deer (B) fungus (C) grass (D) hawk
Example Output:
C