The correct option is B Ronald Ross
Sir Ronald Ross, KCB, FRS, was an Indian-born British medical doctor. On 20 August 1897, in Secunderabad, Ross made his landmark discovery. While dissecting the stomach tissue of an anopheline mosquito fed four days previously on a malarious patient, he found the malaria parasite and went on to prove the role of Anopheles mosquitoes in the transmission of malaria parasites in humans. In 1902 he was awarded the Nobel prize for medicine for his work on malaria, by which he had shown how it enters the organism and thereby had laid the foundation for successful research on this disease and methods of combating it.
So, answer is- 'Ronald Ross'.