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.

Which of the following best represents one particular stage in a life cycle?  
 (A) a fish swimming (B) a seed sprouting (C) a leaf growing (D) a dog eating
B

Which two body systems are involved in inhaling oxygen and exhaling carbon dioxide?  
 (A) endocrine and skeletal (B) excretory and nervous (C) circulatory and respiratory (D) digestive and reproductive
C

A Raleigh man turned on his kitchen faucet and filled a glass with water. When he looked at the water, he thought that it might not be safe to drink, so he called the water company to find out. What factor did the man use to evaluate the safety of the water?  
 (A) pH (B) turbidity (C) nitrate concentration (D) phosphate concentration

B