The second one.
Step-by-step explanation:
For first function y = 2x the rate of change = 2.
Second function: rate of change = (12-6)/(3-1) = 6/2 = 3
Third: it's -0.2.
Fourth: it's  (2.5 -3)/ 1= -0.5.
20
step-by-step explanation: