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]: A population of ground squirrels has established a community in the grasslands of the Great Plains. Temperatures often reach -15°C for most of the winter. What is the most likely behavior the ground squirrels use to survive these winter temperatures?  
 (A) burrowing below the frost point of the soil surface (B) burrowing in tree trunks above the soil surface (C) consuming roots found under the soil surface (D) consuming organisms found in the soil surface
[A]: A


[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


[Q]: Fossil fuels are common sources of energy. What type of pollution is most often associated with burning fossil fuels?  
 (A) air (B) land (C) noise (D) water
[A]:
A