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.

A student wants to organize a group of animals into two categories based on observable external features. Which display will most appropriately show the two categories of animals?     
 (A) a timeline (B) a pie chart (C) a data table (D) a line graph
C

Electron transport in mitochondria results in a chemiosmotic gradient of which particle across the mitochondrial membrane?  
 (A) ADP (B) ATP (C) protons (D) neutrons
C

Falling and rising air and water molecules inside of clouds are believed to be factors in the formation of lightning. Which kind of energy transfer is taking place to cause this weather phenomenon?  
 (A) electrical to thermal (B) thermal to mechanical (C) chemical to mechanical (D) mechanical to electrical

D