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]: Which two behaviors best demonstrate stewardship?  
 (A) reducing consumption, recycling wastes (B) increasing consumption, discarding wastes (C) reducing consumption, discarding wastes (D) increasing consumption, recycling wastes
[EX A]: A

[EX 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.
[EX A]: B

[EX Q]: Sound waves can pass through all of these except  
 (A) air. (B) steel. (C) water. (D) a vacuum.
[EX A]:
D