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: Which would be a safe practice to exercise during laboratory investigations?  
 (A) using open flames to heat all materials (B) keeping your cell phone on the laboratory countertop (C) knowing where your instructor/laboratory leader is at all times (D) removing your safety glasses when moving from station to station

A: C
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Q: A rock sample will most likely contain  
 (A) plants. (B) minerals. (C) water. (D) wood.

A:
B
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