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 agent has analgesic effect also 
Select and explain. 
A. Thiopentone, B. Propofol, C. Etomidate, D. Ketamine
D: Ketamine
Answer: D: Ketamine 
Explanation: Ketamine does not elicit pain on injection, instead produces profound analgesia. Thiopentone at a concentration greater than 2.5% can produce pain on injection and venous thrombosis. Propofol is formulated as a lipid emulsion which causes pain on injection. A new aqueous prodrug, Fospropofol is associated with less pain on injection. Etomidate, although causes pain on injection, the lipid formulation of etomidate is associated with a much less frequent incidence of pain.