Which of the following statements is true regarding hypoxia?

Correct option is B

Cyanosis appears when deoxygenated Hb > 5 g/dl. Hence, it is a late sign of hypoxia, not early. Early signs = restlessness, tachycardia.
Explanation of options: (a) ✘ Early signs = irritability, tachycardia, not cyanosis. (b) ✔ Correct; cyanosis is late manifestation. (c) ✘ Cyanosis can occur in hypoxia if Hb adequate. (d) ✘ In CO poisoning, skin may appear cherry red, not cyanotic.