This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
The major sign of hypoventilation is: 
Select and explain. 
A. Cyanosis, B. Dyspnoea, C. Hypercapnia, D. Hypoxia
C: Hypercapnia
Answer: C: Hypercapnia 
Explanation: In hypoventilation the amount of air moving in and out of lungs is reduced. Hypoventilation results in hypoxia (reduced oxygen availability to cells), hypercapnia (increased CO2 content of blood), dyspnoea (difficulty in breathing) and death. Hypercapnia (sign) stimulates respiratory centre excessively and leads to dyspnoea (symptom).