Two Cars Approach Each Other on a Straight and Level

Multiple Choice

Two cars approach each other on a straight and level road. Car A is traveling at 75 km/h, due north and car B is traveling at 45 km/h, due south. Both velocities are measured relative to the ground.
-What is the velocity of car A relative to an observer in car B?

A) 75 km/h, north
B) 30 km/h, north
C) 30 km/h, south
D) 120 km/h, south
E) 120 km/h, north