The correct option is D Anton von Leeuwenhoek
The first man to witness a live cell under a microscope was Antonie van Leeuwenhoek, who described the algae, Spirogyra, in 1674. He named that cell as animalcules. He is also known as father of microbiology, as he was first to study the microorganism.
So, the correct answer is option D.