Answer:
1. organisms, one, more
2. cell, living
3.cells, pre-existing
Step-by-step explanation:
The cell theory is an important historical scientific theory that is valid and accepted universally that has three major parts about the cell. This theory says that all organisms comprised and build of one or more cells.
This theory also states that the cell is the basic and fundamental unit of all living organisms. Virchow made a contribution to the cell theory later. The third and important part of the cell theory is that all cells are produced by the cell already exist.