In the figure below a charge $+Q$ is located a distance $a$ along the $+y$-axis. A charge $-Q$ is located at $-a$ along the $y$-axis. At a point a distance $a$ along the $x$-axis (marked with an X) we want to know the direction of the net electric field created by the two charges.
Which of the red arrows labeled a through h on the figure best describes the net electric field direction? [Hint: consider the effect of these charges on a small positive test charge at X]