The function of the iris in the eyes of a frog is to

The figure shows parts of the human eye labeled as $A, B, C$ and $D$. Select the option which correctly identifies the labeled part with its function and characteristics.

$A$: Retina is arranged anatomically in reverse order from what might be expected.
$R$: The receptor cells are towards the outside and ganglionic cells towards the inside,and light must pass through the nerve cells to reach them.

The region of the vertebrate eye, where the optic nerve passes out of the retina, is called the

As compared to rods,the cones are ...... times less sensitive.

In humans,presbyopia is an eye defect that occurs with aging,in which ....