Who among the following was one of the early naturalists who studied fossils?

Fossils are ancient organisms' remains or traces that have been preserved in rocks or sediment. 

In 1677, Robert Plot is credited with discovering the first dinosaur bone, but his best guess as to what it belonged to be a giant human. 

It wasn't until William Buckland, the first professor of geology at Oxford University, that a dinosaur fossil was correctly identified for what it was.

Building on the work of Pasteur and Lister, Robert Koch helped to establish bacteriology as a modern science. He discovered the organisms that cause anthrax, septicaemia, tuberculosis, and cholera.
To avoid the dreadful risks of smallpox vaccination, Edward Jenner invented vaccination with cowpox.
Robert Brown was a Scottish botanist who was responsible for discovering the nucleus of the cell as well as the Brownian motion, which is the random movement of microscopic particles.