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 involves the greatest variety of cell types?  
 (A) a tissue (B) an organ (C) an organ system (D) an organism
D

What is the name of the product formed from the reaction shown below? 4Fe(III) + 3O_{2} -> 2Fe_{2}O_{3}  
 (A) iron (II) oxide (B) iron (III) oxide (C) oxygen ferrite (D) diferrous trioxide
B

Two seismographs are placed 500 km from an active fault line, one on each side of the active fault line. During an earthquake, what most likely accounts for the different readings on the seismographs?  
 (A) the pull of gravity on the waves (B) the interaction of light with waves (C) the differences in the strength of the waves' origins (D) the different media through which the waves travel

D