Step1 :
Determine rate of change for each function.
For function b
x1 = 0, y1 = 0
x2 = 2, y2 = 2
For function a
x1 = 0 y1 = 1
x2 = 2 y2 = 4
For function c
x1 = 0 y1 = -1
x2 = 2 y2 = 0
For function d
x1 = 0 y1 = 0.5
x2 = 2 y2 = 2.5
Step 2: Final answer
Function a has the greatest rate of change.