A part of the cell theory is cells come from pre-existing cells. The correct option is A.
The cell theory is the conclusion of many scientists. There are three postulates of the cell theory. They are: all organisms are made up of cells. New cells are made up of old cells, and the cell is the basic structural and functional unit of life.
The cell is the smallest and basic unit of life. All functions of the body are performed by cells. It contains a cell organelle that has different functions and structures.
A nucleus is present in the cell and microscopic organs must have a single cell, they are not a part of cell theory, this is more related to the organism, not cells.
Thus, the correct option is A. cells come from pre-existing cells.
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