Connecting wires carrying currents in opposite directions are twisted together in using electrical appliances in order to reduce.
(A) Electrical effect
(B) Magnetic effect
(C) Seebeck effect
(D) Peltier effect

Hint
We have learnt the concept that affects which are equal in magnitude but opposite in direction will definitely cancel out. We will teach you that concept in this question, as equal currents in the wire are given.

Complete step by step answer
As per the question, the magnetic field will be almost zero when two wires carrying current in opposite directions are twisted together.
The magnetic fields of the consecutive twists can be observed in the opposite directions when the wire is twisted, so the resultant magnetic field will cancel out. The combined effect is about zero over the long length of the wire. Because of wires, the magnetic field will be at a point between the two wires. It is known from that during the first turn, the net magnetic field is equal in magnitude and opposite in direction to the net magnetic field during the second turn of twisted wires, which drives to the cancellation of these fields.
So, when there is a twisted wire, then from the progressive twists, the resultant fields appear in the opposite directions. Hence, over long lengthy twisted wires, the combined effect is approximately zero.

Note
Point to be noted is, as per question we know that in the twisted wires current are flowing in opposite directions and to know the direction of the magnetic field acting on twisted wires we use right-hand thumb rule.
The electric effect is the phenomena in which electrically charged particles are evicted from or within a material when that material absorbs electromagnetic radiation.