Two Cars Start at the Same Point, but Travel in Opposite

Multiple Choice

Two cars start at the same point, but travel in opposite directions on a circular path of radius R, each at speed v. While each car travels a distance less than $\frac{\pi}{2} \mathrm{R}$ , one quarter circle, the centre of mass of the two cars:

A) remains at the initial point.
B) travels along a diameter of the circle at speed v' < v.
C) travels along a diameter of the circle at speed v' = v.
D) travels along a diameter of the circle at speed v' > v.
E) remains at the centre of the circle.