Correct Option: A

Mycobacteriumleprae, the causative agent of leprosy, was discovered by G. H. Armauer Hansen in Norway in 1873. Hansen observed a number of nonrefractile small rods in unstained tissue sections. The rods were not soluble in potassium lye, and they were acid- and alcohol-fast. In 1879, he was able to stain these organisms with Ziehl’s method and the similarities with Koch’s bacillus (Mycobacterium tuberculosis) were noted.