The correct option is B Schwann, Schleiden and Virchow
Cell theory was proposed by a German botanist, Matthias Schleiden and English zoologist, Theodor Schwann in the year 1839. Cell theory was considered as the most acceptable theory which, elucidated the functioning of a cell. The cell theory includes the following points -
1) All living things are made up of cells.
2) The cell is the smallest living thing that can perform all the functions of life.
Later on, in the year 1855, Rudolf Virchow added a new point in cell theory that all cells must come from pre-existing cells, which was also known as "Omnis cellula e cellula". The modern cell theory is called as 'Cell Principle' or 'Cell Doctrine'.
So, the correct answer is option B.