Solution

$$\textbf{Solution:}$$
$$\bullet$$ Cell organelles like mitochondria, ribosomes, nucleus, etc., have specific functions They can not be referred to the functional unit of the cell.
$$\bullet$$ This is because they will perform only specific functions within a living cell. They can not act as units.
$$\bullet$$ The nuclei, on the contrary, have an independent existence. it’s the littlest, structural and useful unit of life.