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: The phases of the Moon are daily changes in the appearance of the Moon. One reason Moon phases occur is because the Moon reflects sunlight. Which is another reason that the phases of the Moon occur?  
 (A) Earth is tilted on the axis. (B) The Moon rises and sets. (C) The Moon orbits Earth. (D) Earth orbits the Sun.
Example Output: C

Example Input: In an ecosystem, not all of the energy that is available is used by the organisms. Some energy becomes unavailable before it can be transferred to organisms in the next trophic level. How does the energy most likely become unavailable?  
 (A) The energy is stored as food. (B) The energy is dissipated as heat. (C) The energy is trapped in dead organisms. (D) The energy is moved to another ecosystem.
Example Output: B

Example Input: On the edge of many deserts, there is a delicate area with abundant vegetation. Sometimes cattle are allowed to graze in these areas. The hooves of the cattle compact the topsoil making it less absorbent. Which environmental concern is most likely to happen at the edge of the desert when cattle graze there?  
 (A) erosion (B) nutrient depletion (C) atmospheric heating (D) groundwater contamination
Example Output:
A