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: Many scientists are convinced that an increase of certain gases in the atmosphere is affecting global temperatures. What makes this hypothesis difficult to prove?  
 (A) Trees absorb these gases. (B) Global temperatures are rising. (C) Many variables affect global temperatures. (D) Many human activities produce these gases.

A: C
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Q: What tool would be used to examine a fingerprint?  
 (A) a graduated cylinder (B) a hand lens (C) a pair of goggles (D) a thermometer

A: B
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Q: Miriam notices when she goes to the beach that sometimes the water rises as high as the pier. At other times of the day, the water barely covers the pillars under the pier. These differences in water level are primarily due to the gravitational influence of which of the following?  
 (A) the Sun (B) the Moon (C) asteroids (D) comets

A:
B
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