Correct Answer: (d) Nitrous oxide
Solution:Anaesthetic substances are mainly used for decreasing the sensation or awareness. William Mortan has used it for the first time in 1846 in the form of di-ethyl ether. In 1847, Jams Sampson used chloroform as an anaesthetic. Chloroform, Nitrous oxide, pentothal sodium, halothien, chloropropane, cocaine etc. are used as an anaesthetic.