Which parts are included in the labyrinth?

The $Oval$ $Window$ (fenestra ovalis) is an opening of the .....

Read the following statements regarding the structure of the human ear and select the correct option.
Statement $I$: The tympanic membrane is covered with mucous membrane on the inner side,to the surface of which is attached the $1^{\text{st}}$ ear ossicle,namely the incus.
Statement $II$: Scala vestibuli and scala tympani are filled with perilymph and form a part of the cochlea.

Which of the following is a part of the middle ear?

Which bone is in contact with the $fenestra \text{ } ovalis$?

The sound waves produce vibrations in the endolymph,which in turn affects one of the following to produce the stimuli for hearing: