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]: Where do good bacteria grow to help keep people healthy?  
 (A) in the brain (B) in the blood (C) on the skin (D) on the bones
[EX A]: C

[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]: Which of these geographic features most directly influences the climate of Nevada by limiting the amount of water vapor that can reach the state and fall as rain?  
 (A) Pacific Ocean (B) Colorado River (C) Sierra Nevada Mountains (D) Columbia River Basin
[EX A]:
C