Professor Tompkins Notices That Rats Run Quickly Through a Maze

Multiple Choice

Professor Tompkins notices that rats run quickly through a maze when exposed to loud noise. Which of the following is necessary to transform this observation into a two-group experimental design?

A) multiple comparison conditions where rats run through mazes while exposed to several different volumes of noise
B) multiple rats to observe running through the maze with loud noise
C) a control condition where rats run through a maze without exposure to loud noise
D) a subjective way to measure how fast a rat runs