The sound-producing organ of a bird is:

The lungs are covered by a double-layered membrane known as the pleura. What is the inner layer,which is in contact with the lung surface,called?

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

Choose the correct sentences for the conducting part of the respiratory system.
$(I)$ Transports the atmospheric air to the alveoli.
$(II)$ Clears it from foreign particles.
$(III)$ Humidifies the air.
$(IV)$ Brings the air to body temperature.

The structure which prevents the entry of food into the respiratory tract is

Which of the following serves as a common passage for both swallowing food and breathing?