Hi! Answer is "the initial velocity of the runner was 4 m/s, and the runner stopped after 8 seconds".
This is a velocity - time graph.
At t = 0 s, the graph has a velocity as 4 m/s. This means, the runner has an initial velocity as 4 m/s.
At t = 4 s, the runner has reached his maximum velocity as 8 m/s and acceleration is 1 m/s².
After t = 4 s, the velocity has decreased with the time means it is a negative acceleration.
At t = 8 s, the velocity of the runner has reached to zero means runner has stopped after 8 seconds.