The mammalian middle ear contains three ossicles, which move the vibrations of the eardrum into waves in the liquid and membrane of the inward ear. There are three ossicles in every ear : Malleus, Incus, Stapes. As we have a couple of ears, so altogether there are 6 ossicles, or 3 sets of ossicles.

The secondary coil is also generating a magnetic field that is growing and shrinking just like the field in the primary coil. This coupling of magnetic energy between these two coils is called mutual induction.

So the correct answer is 'Eichhornia crassipes' An aquatic plant introduced from America to check pollution turned out to be a troublesome weed in Indian water bodies.