Harry conducted an experiment to determine the amount of school buses that passed him on the highway. In his experiment, Harry made a note of all of the school buses that passed him on the highway each day for a week (7 days). He noted the number of buses and time of day (from a 24-hour clock) and created a scatterplot of the information. According to the scatterplot, there is [DROP DOWN 1] between the hour of the day and the number of school buses. Causation [DROP DOWN 2] be determined.