Casey and Mark Are Running a Race at Constant Speeds

Multiple Choice

Casey and Mark are running a race at constant speeds. The graph below shows the distance d (in miles) they have traveled since they started the race at time t (in minutes) . Which one of the following statements is true?

A) Not enough information
B) Mark is running faster than Casey.
C) Casey is running at 0.23 mph, while Mark is running at 0.31 mph.
D) Casey is running at 4.3 mph, while Mark is running at 3.2 mph.
E) Casey and Mark are both traveling at the same constant speed.