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: Anaesthesia
True about endotracheal intubation is: 
Select and explain. 
A. It reduces normal anatomical dead space, B. It produces decrease in resistance to respiration, C. Subglottic edema is most common complication, D. All of the above
A: It reduces normal anatomical dead space
Answer: A: It reduces normal anatomical dead space 
Explanation: A i.e. It reduces the normal anatomical dead space - Endotracheal tube decreases the anatomical dead space (150 ml) to as less as 25 ml. - Endotracheal intubation increases the resistance to respiration; obstruction from kinking, foreign body or secretions fuher increase resistance. Subglottic edema, though a complication, is not the most common one.