21.
 The table below shows some values of a function
 x f(x)
 0 -24
 1 -13
 2 -4
 3 3
 4 8
 5 11
 6 12
 7 11
 8 8
 9 3
 Which of the following BEST shows the values in the domain when the function is increasing?
 A. between 0 and 6
 B. between 3 and 9
 C. between 3 and 6 
 D. between 6 and 9