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]: 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.
[EX A]: B

[EX Q]: Compared to Earth, the Moon is  
 (A) drier. (B) larger. (C) heavier. (D) brighter.
[EX A]: A

[EX Q]: Acid rain can damage limestone buildings and marble statues. It can also harm organisms living in ponds and other ecosystems. Which pollutant in the atmosphere causes most of the acid rain?  
 (A) fluorocarbons from aerosol spray cans (B) nitrous oxide from volcanic eruptions (C) sulfur dioxide from burning fossil fuels (D) soil particles from the use of farm equipment
[EX A]:
C