The graph shows the student's distance in miles from the recreation center after riding the bike x minutes.

What is the domain of the function for this situation?
A. All real numbers greater than or equal to 0 and less than or equal to 28.
B. All real numbers greater than or equal to 0 and less than or equal to 9.
C.{0,4,8,12,16,20,24,28}
D.{0,1,2,3,4,5,6,7,8,9}​