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.

The melting point of a compound was measured by three different scientists. It is acceptable for the scientists to display the same data differently because  
 (A) multiple methods are acceptable for organizing data. (B) melting point data is inconsistent. (C) the scientists collected data in different areas. (D) the data was measured with different instruments.
A

Which example best shows structures that make up the digestive system in the human body?  
 (A) heart, blood, vessels (B) nose, trachea, lungs (C) brain, spinal cord, nerves (D) esophagus, stomach, intestines
D

Which is the most appropriate unit for expressing the distance that an airplane travels in 2 hours?  
 (A) meter (B) kilometer (C) millimeter (D) centimeter

B