In birds,the sound is produced by which of the following?

Diaphragm is a dome-shaped muscular structure which separates

Which respiratory pigment contains $Fe$ and is red in color?

During the intake of food,what prevents the entry of food into the glottis (opening of the windpipe)?

Identify the component of the respiratory system which displays the features given below and choose the correct option:
$I.$ Double layered
$II.$ Fluid contained in it reduces the friction on the lung surface
$III.$ Its outer layer is in contact with the thoracic wall
$IV.$ Its inner layer is in contact with the lungs

What are the membranes covering the lungs called?