Start from the meaning of the term. Hydrops means an abnormal accumulation of fluid, and here it is the endolymph swelling the membranous labyrinth of the inner ear. The single condition that this pathological hallmark belongs to is Meniere's disease.
Clinically the swollen endolymphatic space explains the disease picture: recurrent spinning vertigo, hearing that rises and falls, ringing in the ear, and a sense of pressure or fullness. The fluid overload disturbs both the cochlear and vestibular functions, producing this combined symptom set.
The other options have entirely different mechanisms. Otosclerosis is a bony fixation problem at the stapes giving conductive loss; acoustic neuroma is a nerve sheath tumour; cholesteatoma is trapped skin debris in the middle ear. None of them is built around fluid distension of the labyrinth. Thus the correct match is Meniere's disease.
\[\boxed{\text{Meniere's disease}}\]