What is the average rate of change for the sequence shown below?

coordinate plane showing the points 1, 4; 0.5, 3.5; 0, 3; and negative 0.5, 2.5

−2
−one half
1
2

Let's pick on two points. Let's say we pick the first two points which are (1,4) and (0,5,3.5)

The slope formula tells us that

m = (y2-y1)/(x2-x1)
m = (3.5-4)/(0.5-1)
m = (-0.5)/(-0.5)
m = 1

So the slope is 1. We can pick any other two points, run them through the slope formula, and we'll get the same result. 

So that's why the answer is choice C) 1