she went 8 km and the displacement was 6 km
velocity = displacement / time
displacement measures how far the ending point is from the starting position. if the object returns to its original position, displacement will be 0 m.
in the question, the object starts at p and returns to p, so displacement equals 0 m. thus, no matter how long the travelling time is, the average velocity is also 0 m/s.
so, the ans is a.