Question

The cell theory states that
A. All cells have nuclei.
B. All cells are totipotent.
C. Cells reproduce by mitosis.
D. Cells are the basic structural units of living beings.

Answer 1

Hint: The cell theory clearly suggests the fundamentals of biology and therefore it applies to each living organism and is considered to be universally true.

Complete answer: Cell theory was put forward by a famous German botanist- Matthias Schleiden and an English zoologist- Theodor Schwann in the year 1839.
It has the following propositions:
1) Cells are the basic unit of life and they are therefore considered to be the building blocks of living organisms.
2) All the living organisms are made up of cells; a cell is the basic structural and functional unit of each living organism.
3) All cells are produced by cells that already pre-exist.

Additional information: The cell is the smallest structural and functional compartment of living organisms, which can exist on its own.
Therefore, it is many times called the building block of life.
Some organisms, such as bacteria/ yeast, are unicellular—containing only a single cell—while others, for instance, mammalians, are multicellular in nature.

Therefore, the correct answer is option D. Cells are the basic structural units of living beings.

Note: The cell theory is universal and it helped in shaping modern biology.
Rudolf Virchow, later on, suggested some modifications to it.
In 1838 Schleiden defined the cell as the basic unit of plant structure.