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 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.

Ex Output:
B


Ex Input:
If the solar system were used as a model of an atom, what would the Sun most likely represent?  
 (A) an ion (B) a nucleus (C) a neutron (D) an electron

Ex Output:
B


Ex Input:
How does the buying and selling of a popular species of rainforest animal as pets have a negative effect on the rainforest ecosystem?  
 (A) The rate of photosynthesis may decrease. (B) There is a probability of genetic variability. (C) The number of symbiotic relationships increases. (D) It could lead to the potential extinction of those animals.

Ex Output:

D