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: Which unit is used to express the amount of energy in food?  
 (A) Calorie (B) degree Celsius (C) milliliter (D) gram

A: A
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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 of these is most likely to be spread when two people drink from the same water bottle?  
 (A) asthma (B) malaria (C) strep throat (D) hay fever

A:
C
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