If you take the Western direction as the positive direction and the Eastern direction as negative one, then,
Distance traveled to the West = +15 m
Distance traveled to the east = (-2 m) + (-7 m ) = -9 m
Total Displacement = 15 m + (-9) m
Total displacement = 6 m
Since the total displacement is positive, the displacement will be in the Western direction.
So, option (D) is correct.