Aschool has collected student enrollment data since it opened. the graph below shows the number of students (y), in hundreds, enrolled at the school each year (x) the school has been open.

which statement best describes the change in student enrollment shown in the graph?

a. enrollment has increased by approximately 400 students per year.
b. enrollment has increased by approximately 1.3 students per year.
c. enrollment has increased by approximately 133 students per year.
d. enrollment has increased by approximately 1,100 students per year.