Answer:
the slope of the line on a velocity vs. time graph represents acceleration
Step-by-step explanation:
Acceleration is equal to the ratio between the change in velocity of an object and the time taken:

On a velocity-time graph, this ratio corresponds to the slope of the line. In fact,
corresponds to the increment in the y-value (the velocity), while
corresponds to the increment in the x-value (the time), therefore their ratio corresponds to the definition of slope of the line.