Site of gaseous exchange in lungs is

Correct answer: (d) Alveoli

Explanation

Alveoli are tiny air sacs in the lungs where oxygen and carbon dioxide are exchanged with the blood.

Their thin walls and rich capillary network allow rapid gaseous exchange.

Bronchioles only carry air to the alveoli; the pulmonary vein returns oxygenated blood; tracheoles belong to insect respiration.