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.

When microorganisms deplete the oxygen in soil through respiration, the soil becomes  
 (A) humus. (B) anaerobic. (C) compost. (D) aerobic.
B

Which of these will most likely result from small meteoroids entering the atmosphere of Earth?  
 (A) a decrease in air temperature (B) the appearance of shooting stars (C) an decrease in atmospheric ozone (D) the appearance of the Northern Lights
B

Which of the following correctly explains how atmospheric nitrogen is converted to nitrogen compounds used by living organisms?  
 (A) Sunlight converts atmospheric nitrogen to a form usable by protists. (B) Plant leaves convert atmospheric nitrogen to a form usable by animals. (C) Bacteria in soil convert atmospheric nitrogen to a form usable by plants. (D) Invertebrate animals in soil convert atmospheric nitrogen to a form usable by fungi.

C