Which graph has a rate of change of zero?

Step-by-step explanation:

On the other hand, the vertical line has an undefined slope.

Slope is rise/run or change n y over change in x.

If the y axis coordinate never changes, then rise = 0. The only number that changes is x. x changes 1 for every 0 y changes. 0/1 = 0.

In a vertical line, however, the x coordinate is the one that doesn't change. We reverse the number from before, but we have a problem 1/0 is an undefined number since you cannot divide by 0.

Answer is second graph shown