The correct option is D. Micheal Friday devised a wire which hanged down into a glass vessel that has a bar magnet secured at the bottom. He then filled the glass vessel with Mercury and connected the apparatus to a battery. This sent electricity through the wire, thus creating a magnetic field around it. This field interacted with the field around the magnet and cause the wire to rotate clock wisely.
Standing waves can be thought of as a sin wave and a cos wave overlapping each other. They go in different direction hence Cis correct
Wave interference can be thought of as the opposite of destructive ---> constructive anda hencd meet and interact on the same medium such that answerBis correct
