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.

[EX Q]: In an accurate diagram of the solar system, which object would be shown closest to Earth?  
 (A) the Moon (B) the asteroid belt (C) Mars (D) Saturn
[EX A]: A

[EX Q]: Some plant species are more tolerant of acidic soil than others. The tolerant species are favored in areas affected by which consequence of human activity?  
 (A) mixing of pollutants with rain (B) erosion of topsoil by clearcutting (C) runoff of fertilizer used in farming (D) thinning of the atmospheric ozone layer
[EX A]: A

[EX Q]: Which is the best way a science student can help to maintain laboratory equipment?  
 (A) perform investigations using only new materials (B) throw away glass items after investigations are complete (C) clean up all materials and workspaces after investigations (D) eat in the laboratory only after investigations are complete
[EX A]:
C