Answer:
All of the above.
Explanation:
In a graph, the unit rate gives us the change in y for a unit change in x. That is, the unit rate is the rate of change in y when the change in x is 1.
Therefore, the unit rate is the same as the rate of change.
And the rate of change is synonymous with the slope.
The constant of proportionality is simply the slope/rate of change for proportional equations.
Therefore, the constant of proportionality is also another word for the unit rate.
Our answer is hence all of the above.