Four Charged Particles (Two Having a Charge +Q and Two

Four charged particles (two having a charge +Q and two having a charge -Q) are arranged in the xy-plane as shown in the figure. The charges are all equidistant from the origin. The amount of work required to move a positively charged particle from point P to point O (both of which are on the z-axis) is

A) zero.
B) positive.
C) negative.
D) depends on the path in which the charged is moved.