A. Oxygen
A.
B. Cilia
B.
C. Surfactant
C.
D. Mucus
D.
Correct Answer: C
সঠিক উত্তর: C
Explanation
ব্যাখ্যা
Surfactant is a lipoprotein produced by type II alveolar cells that lines the alveoli and reduces surface tension, preventing them from collapsing during exhalation.