Internal ear is filled with
A. Perilymph
B. Endolymph
C. Lymph
D. Both A and B

Hint: The ear is the listening organ and, in mammals, it also helps in balancing. The ear is commonly defined in mammals as having three parts: the outer ear, the middle ear, and the inner ear. The pinna and the ear canal are composed of the outer ear.

Complete answer:
The middle ear is the area of the ear between the circular window and the eardrum. From the outer ear, the middle ear transmits sound to the inner ear. The hammer (malleus), the anvil (incus) and the stirrup (stapes), the oval window, the round window, and the Eustachian tube are the structures present in the middle ear. The inner ear, also known as the ear labyrinth, is part of the ear that comprises the sense of hearing and equilibrium organs. The bony labyrinth is the inner ear's cavity. The central vestibule, the semicircular canals, and the cochlea are part of the bony labyrinth. A complex membrane sac, called the membranous labyrinth, lies within the bony labyrinth. A fluid called perilymph is filled between the wall of the bony labyrinth and the wall of the membranous labyrinth. The space inside the membranous labyrinth is filled with endolymph.

Therefore the answer will be option D.

Note:
 The sound waves induce vibration of the eardrum, which sets in motion the three small bones in the middle ear. The motion of the bones allows fluid to travel in the inner ear or cochlea. The inner ear fluid movement induces bending of the hair cells in the cochlea. The hair cells transform the movement into electrical pulses. These electrical impulses are transmitted to the auditory (hearing) nerve and then to the brain, where they are interpreted as sound.