Identify the correct statement regarding the human respiratory system:
A. The diaphragm is made of smooth muscle.
B. Pulmonary veins carry deoxygenated blood.
C. The trachea is also called the voice box.
D. Alveoli are the main sites of gas exchange.
Answer: Option D
Solution (By JKSSB Mock Tests)
Alveoli are thin-walled air sacs where O₂ and CO₂ exchange occurs. The voice box is the larynx; diaphragm is skeletal muscle; pulmonary veins carry oxygenated blood.
Explanation:
Tidal volume (TV) is the amount of air breathed in or out in one normal respiratory cycle, about 500 mL in a healthy adult. Vital capacity is the maximum air exhaled after a maximum inspiration. Total lung capacity is the total volume of air lungs can hold. Residual volume is the air remaining in lungs after maximum expiration to prevent alveolar collapse.
Explanation:
Nitrogen is an essential component of amino acids (proteins) and nitrogenous bases of nucleic acids (DNA, RNA). Phosphorus is in nucleic acids and ATP, potassium is an ion, calcium is structural. The nitrogen cycle makes atmospheric N₂ available to organisms through fixation.
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