This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Intravenous Anesthetic Agents, Subject name: Anaesthesia
Which intravenous anaesthetic can be used for upper airway manipulation in absence of neuromuscular blockers- 
Select and explain. 
A. Thiopentone, B. Propofol, C. Etomidate, D. Ketamine
B: Propofol
Answer: B: Propofol 
Explanation: Propofol - induced depression of upper airway reflexes exceeds that of any other agent thus allowing intubation, endoscopy or laryngeal mark placement in absence of neuromuscular blockers. ketamine preserve upper airway reflexes.