The correct option is B De Graaf
Karl Ernst von Baer was the first to discover the egg of the mammal in the ovary.
Regner de Graaf discovered follicles in the human ovary in 1671 and considered them to be eggs. Since Graaf discovered follicles, they are also called as Graafian follicles.
Robert Brown named the cell nucleus in 1827.
Spallanzani was the first to disprove spontaneous generation theory. Thus, the correct answer is option B.