Marie is doing a science experiment in which she rolls a ball down an aisle and observes how far the ball travels per second.
 What does the point (0,0) on the graph represent?
 A. 
 The ball rolls 0 feet in 0 seconds.
 B. 
 The distance traveled does not vary with time.
 C. 
 The unit rate is 0 feet per second.
 D. 
 The distance traveled is constant after the ball is rolled.