Two wires carrying currents $I_1, I_2$ lie, one slightly above the other, in a horizontal plane as shown in figure. The region of vertically upward strongest magnetic field is:

Explanation: 

Since the two currents have the same magnitude, the magnetic field produced by each current-carrying wire will have the same strength in every region. The direction of the two currents is indicated in blue and red in the diagram. Based on these directions, the resulting magnetic field in each region will align as specified for each current. The magnetic fields in opposite directions cancel each other out, leaving no net magnetic field in those areas. As a result, the net magnetic field is strongest in regions A and D. In region A, the magnetic fields generated by both current-carrying wires are directed out of the page, combining constructively. Therefore, region A has the strongest magnetic field directed out of the page.