Which pigment helps some nocturnal animals to see during the night?

The cones are located in

Which of the following statements is correct regarding the pupil of the human eye?
$(I)$. It is the aperture surrounded by the iris.
$(II)$. The diameter of the pupil is regulated by the muscle fibres of the iris.
$(III)$. It is a transparent crystalline structure attached to the ciliary body.
The correct option is:

$X -$ Rod cells' function is twilight (scotopic) vision.
$Y -$ Cone cells' function is daylight (photopic) vision.

The cavity of the vitreous humour in the eyes is situated:

How many types of cones are present which are responsible for the colour differentiation?