The Figure Shows Two Sets of Water Waves, Created by Two

The figure shows two sets of water waves, created by two sources labeled "A" and "B." The solid half- circles represent wave crests from A, and the dashed half- circles represent wave crests from B. Suppose that individual wave crests from either source A or source B alone are 5 mm above the level of the undisturbed water. Then the displacement of the water [above or below the level of the undisturbed water] at the point marked "x" [with the arrow pointing toward it] is

A) 0 mm.
B) +10 mm.
C) - 10 mm.
D) - 5 mm.
E) +5 mm.