As part of a science project, Andy surveys several students in his class to determine their energy levels throughout the day. He asks the students to rate their energy level on a scale from 1 to 10, where 10 is the highest energy level possible and 1 is the lowest energy level possible. Andy then finds the average energy level for the class for each hour after the school day begins until the end of the day. He graphs his data as shown below.
He observes that students seem to have less energy as the day progresses.
Which of these statements is true?

A. Andy’s study shows causation.
B. Andy’s study shows correlation.
C. Andy’s study shows both correlation and causation.
D. Andy’s study shows neither correlation nor causation.