You are given a science question (hard-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: Which of the following actions will increase the gravitational force between two masses, m_{1} and m_{2}, by the greatest amount?  
 (A) Halve the mass of m_{1} and halve the distance between m_{1} and m_{2}. (B) Halve the mass of m_{1} and double the distance between m_{1} and m_{2}. (C) Double the mass of m_{1} and halve the distance between m_{1} and m_{2}. (D) Double the mass of m_{1} and double the distance between m_{1} and m_{2}.

A: C
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Q: Scientists have measured the rate of growth of the Atlantic Ocean basin to be about 2 to 3 cm per year. This type of activity coincides with the formation of ridges on the ocean floor. What is the most likely cause of this activity?  
 (A) erosion from tidal action (B) the deposition of sediment (C) the flow of continental basalt (D) movement from tectonic plates

A: D
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Q: In some U.S. national parks, black bears have lost their fear of humans and look for food near campsites along the roadside. This is an example of an animal  
 (A) becoming an herbivore. (B) using its inherited traits. (C) finding a new ecosystem. (D) learning a new behavior.

A:
D
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