Which is the respiratory organ of a silkworm?

Which of the following modes of respiration always continues in a frog?

In which of the following is the skin an accessory respiratory organ?

Match the Column $I$ with Column $II$ and select the correct option:

Column $I$ (Animals)	Column $II$ (Respiratory organs)
$i$. Sponges	$a$. External gills
$ii$. Insects	$b$. Plasma membrane
$iii$. Limulus	$c$. Tracheae
$iv$. Amphibian tadpoles	$d$. Book gills

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

For gaseous exchange,plants have: