A q q SolutionElectric Field due to Lower right q Charge is

Solution

Electric Field due to Lower right -q Charge is in the Direction of C.
Electric Field due to Upper left -q Charge is in the Direction of A.

The Cos componenets of both these field will add , while the sin component will be cancelled.
So Now Net Electric Field due to these two charges will point in the direction of B.

Electric Field due to +q Charge is in the direction of D.

But As the Magnitude of combined Electric Field due to A&C > That of B.

Therefore Net Electric Field will Point in the Direction of B.