Which pair of sentences is describing the same velocity?

a.A car is parked. A car is moving in circles.

b.A bus drives 40 miles per hour north. A truck drives 50 miles per hour north.

c A boy walks east at 6 kilometers per hour. A girl walks west at the same speed as the boy.

d.Valerie rides her bike south at 8 kilometers per hour. Owen jogs south at 8 kilometers per hour.