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.

Q: When do mutations help make an ecosystem more sustainable?  
 (A) when mutations decrease the number of individuals in an ecosystem (B) when mutations increase the number of individuals in an ecosystem (C) when mutations decrease the number of species in an ecosystem (D) when mutations increase the number of species in an ecosystem

A: D
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Q: Which is the best evidence for the theory of continental drift?  
 (A) the appearance of volcanoes at the boundaries where plates collide (B) earthquakes at boundaries where one plate slides past another (C) cases where a species exists in only one isolated place (D) fossils of the same species found on widely separated continents

A: D
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Q: Which of these is a renewable resource found in Nevada?  
 (A) zinc metal (B) gravel deposits (C) petroleum products (D) geothermal energy

A:
D
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