Question

The line on this graph represents an in-line skater's distance traveled over time. From the graph, you can tell that the skater travels at a constant speed. What is the speed? (Hint: Dividing distance by time gives the speed, which is the same as the slope of the line.)
A). 10 mi/h
B). 0.1 mi/h
C). 25 mi/h
D). 15 mi/h