Concept:
Electric field at centre due to each charge is along the line joining the charge and centre.
Step 1: Charges
\[
A(+q),\; B(-2q),\; C(-q),\; D(+2q)
\]
Step 2: Directions of fields
• Positive charge → field away from charge
• Negative charge → field towards charge
Step 3: Vector addition
Resolve all four contributions:
- Fields from opposite corners do not completely cancel due to unequal magnitudes
- Net resultant points in upward diagonal direction
Step 4: Final direction
Resultant electric field is along a direction making \(45^\circ\) with OA upward.
\[
\therefore \text{Answer is (A)}
\]