Concept:Use coordinate geometry to find relative positions.Explanation:Let A be at (0,0).D is 12 km north of A: D = (0,12).C is 15 km west of D: C = (−15,12).B is 15 km west of A: B = (−15,0).Distance from C to B: difference = (−15−(−15),0−12)=(0,−12).Thus B is 12 km south of C.Answer:D. 12 km towards South