Concept:Endolymph is the fluid filling the membranous labyrinth inside the inner ear.
Explanation:Within the inner ear, the membranous labyrinth lies inside the bony labyrinth and the space inside the membranous labyrinth contains endolymph.
The semicircular canals, the utriculus, and the sacculus are all parts of this membranous labyrinth, so endolymph is present in each of them.
The tympanum, however, is a part of the middle ear that conducts sound vibrations.
It is not connected to the membranous labyrinth and therefore does not contain endolymph.
Answer:C. Tympanum