In Fig.1.1, two positive charges q2 and q3 fixed along the y axis, exert a net electric force in the +x direction on a charge q1 fixed along the x axis. If a positive charge Q is added at (x, 0), the force on q1
(a) shall increase along the positive x-axis.
(b) shall decrease along the positive x-axis.
(c) shall point along the negative x-axis.
(d) shall increase but the direction changes because of the intersection of Q with q2 and q3.