Which of following is not a tenet of the cell theory?

A. The cell is the structural unit of life.

B. Cells can only arise by division from a pre-existing cell.

C. All organisms are composed of one or more cells.

D. All cells must have a nucleus.

D. All cells must have a nucleus

Explanation:

According to the tenets of the cell theory:

a. the cell is the structural unit of life, in other words without the cell there is no life;

b. Reproduction cannot occurs without cell division, hence cells can only arise by division from a preexisting cell;

c. All organisms are composed of one or more cells, prokaryotes are referred to as singled celled organisms while eukaryotes are referred to as multi-cellular organisms;

d. Not all cells must have a nucleus. There are two major types of cells; the prokaryotic cells and the eukaryotic cells. Eukaryotic cells have a well defined nucleus and other membrane bound organelles, while prokaryotic cells do not have a defined nucleus and other membrane bound organelles. Notwithstanding, they both contain genetic materials.