Three Equal Negative Point Charges $- q$ Are Placed at Three of the Corners of a Square

Three equal negative point charges $- q$ are placed at three of the corners of a square of side $d$ as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square?

A) $\mathrm { A }$
B) $B$
C) $\mathrm { C }$
D) $\mathrm { D }$