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: Some of the new cars being made can run on a renewable fuel that is made mostly from corn. Scientists are developing even more renewable fuels to replace gasoline. Why are renewable fuels most likely becoming more important?  
 (A) Renewable fuels release less energy. (B) Car fuel tanks are being made smaller. (C) The demand for gasoline is decreasing. (D) Nonrenewable fuel supplies are limited.

A: D
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Q: How does a parachute sufficiently increase air resistance to allow the parachutist to land safely?   
 (A) by decreasing the force of gravity acting on the parachutist (B) by decreasing the total mass of the parachutist (C) by increasing the surrounding air pressure around the parachute (D) by increasing the total surface area of the parachute

A: D
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Q: A container is filled with a mixture of sand and an unknown substance. What should a student do to determine whether iron particles are in the mixture?  
 (A) heat the mixture (B) filter the mixture (C) pour water into the mixture (D) pull a magnet through the mixture

A:
D
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