The phrase “Omnis cellula e cellula” was given by
A) Virchow
B) Pasteur
C) Schleiden
D) Brown

Hint:Cells are the basic and functional unit of any living organism. The phrase “Omnis cellula e cellula” means all living cells arise from the pre-existing cells.

Complete answer:
Let’s discuss each option to analyse the correct option.
>Option A: A German biologist Rudolph Virchow observed that all living cells arise from pre-existing cells ('Omnis cellula e cellula') which was added to the cell theory as a doctrine. Cells are the functional unit of an organism. Two German biologists M. J. Schleiden (1838) and Theodore Schwann (1839), proposed the cell theory. According to the theory, all living organisms are composed of cells, which are the smallest entities that can be called 'living'. Therefore, this is the correct option.
>Option B: Louis Pasteur was a famous French microbiologist. He discovered vaccination, fermentation, and Pasteurization. He was the first to discover vaccines for rabies and anthrax. Therefore, this is an incorrect option.
>Option C: M.J. Schleiden, a German botanist announced that all plants were composed of cells. In 1831 German Biologist Theodore Schwann stated that all animals were also formed of cells. He also observed that except for cell walls, plant cells and animal cells were similar. Thus, their combined observations lead to the formulation of cell theory. Therefore, this is an incorrect option.
>Option D: Robert Brown, scotch botanist discovered the nucleus in an orchid root cell. He also observed that cells were surrounded by cell membranes. Therefore, this is an incorrect option.

Thus, the correct answer is option (A) Virchow.

Note:It is to be noted that Rudolph Virchow’s cell principle is also referred to as modern cell theory. According to cell principle life exists only in cells, life passes from one generation to another in the form of cells, called gametes.