The laryngopharynx opens into

Which of the following prevent the collapsing of the trachea?

In humans,the oblique fissure is present in

Which membrane covers the lungs and provides protection?

Two friends are eating together at a dining table. One of them suddenly starts coughing while swallowing food. This coughing action is likely due to the improper movement of the .......... .

The diagram of the human respiratory system is given below. What are $P$ and $Q$?
$\quad P \quad\quad Q$