Question

A runner maintains a constant velocity of +3.0 m/s. Which of the following position-time graphs shows the runner’s location from the starting point at 5.0 s intervals for 30.0 s?

Answer 1

3 meters a second.
Every 5 seconds, that runner should run 5*3=15 meters (distance = average velocity times time).

That means that your slope must be 15meters / 5 seconds.
Look for a slope of 15 meters for every 5 seconds.

B seems to fit that description, no?