Why is breathing an involuntary process? Differentiate between cellular respiration and breathing.

Name the following and label them in the given diagram.

(A) Actual site of gaseous exchange

(B) Part that allows air to enter the body

(C) Spongy, bag-like elastic organs

Crossword puzzle

Across ($\to$):

1. Lungs are protected by it.

2. It is present at the entrance of the trachea.

Down (↓):

3. It is a common passage for air and food.

4. Air enters the body through it.