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 cut to the skin is treated with antiseptic first to avoid  
 (A) an immune response. (B) a bacterial infection. (C) bruising of tissues. (D) an allergic reaction.

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

A: B
****
Q: Which statement correctly describes a relationship between two human body systems?  
 (A) The digestive system absorbs nutrients which are transported by the nervous system. (B) The digestive system absorbs nutrients which are transported by the circulatory system. (C) The circulatory system exchanges gases which are transported by the nervous system. (D) The circulatory system exchanges gases which are transported by the digestive system.

A:
B
****