The cochlea is primarily responsible for:

The organ of Corti is not located in the endolymph of which of the following?

Helicotrema is

Match the columns and select the correct option:

$(a)$ Organ of Corti	$(i)$ Connects middle ear to pharynx
$(b)$ Cochlea	$(ii)$ Coiled portion of the labyrinth
$(c)$ Eustachian tube	$(iii)$ Attached to the oval window
$(d)$ Stapes	$(iv)$ Located on the basilar membrane

$(a)\quad (b)\quad (c)\quad (d)$

$P$ is a continuous tubular structure. Inside these tubes, $Q$ is arranged.
$\quad\quad\quad P \quad\quad\quad Q$
$(A)$ $Scala \text{ vestibuli} \quad$ $Scala \text{ media}$
$(B)$ $Scala \text{ media} \quad$ $Scala \text{ tympani}$
$(C)$ $Scala \text{ tympani} \quad$ $Scala \text{ media}$
$(D)$ $Scala \text{ media} \quad$ $Scala \text{ vestibuli}$

Describe the mechanism of hearing briefly.