You are given a science question (hard-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.
--------
Question: How many basic units of information in a DNA molecule are required to encode a single amino acid?  
 (A) 1 (B) 2 (C) 3 (D) 4

Answer: C


Question: While collecting wildflowers, a student begins to sneeze and has itchy, watery eyes. What bodily system causes this reaction?  
 (A) immune (B) nervous (C) muscular (D) circulatory

Answer: A


Question: Sound waves travel fastest in  
 (A) air. (B) iron. (C) water. (D) a vacuum.

Answer:
B