Two identical positive point charges +Q are held fixed on the x–axis at x = −d and x = +d. Point P is located at (0, 2d) on the y–axis. Which of the following best describes the direction of the net electric field at point P?
a) Straight rightward along +x direction
b) The net electric field is zero at P
c) Straight upward along +y direction
d) Straight downward along −y direction