The skin is a respiratory organ in ...........

Which of the following pairs correctly represent an animal and its respiratory organ?
$(a)$ Silverfish $-$ Trachea
$(b)$ Scorpion $-$ Book lungs
$(c)$ Sea squirt $-$ Pharyngeal gills
$(d)$ Dolphin $-$ Skin

Skin of man cannot act as a respiratory organ because

What is the unique feature of the respiratory system of birds?

Which of the following is a simple respiratory organ?

Match the following columns:

Column-$I$ (Plant Part)	Column-$II$ (Gas Exchange Structure)
$P$. Leaves and young stems	$I$. Lenticels
$Q$. Woody stems	$II$. Stomata
$R$. Roots	$III$. Root hairs