Which of the following statements about the cells of living organisms is/are correct ?
A. All are microscopic and cannot be seen with a naked eye.
B. All have a cell wall.
C. All have a nuclear membrane.
D. All have a cell membrane.
Choose the correct option :

The correct option is Only D.

Let us analyze each statement to determine which of them are correct regarding the cells of living organisms:

Statement A: "All are microscopic and cannot be seen with a naked eye."
This statement is incorrect. While most cells are microscopic and require a microscope to be seen, some single cells are large enough to be seen with the naked eye. For example, an ostrich egg is a single cell that can easily be seen without a microscope.

Statement B: "All have a cell wall."
This statement is incorrect. Cell walls are present in plant cells, fungi, bacteria, and algae, but they are completely absent in animal cells.

Statement C: "All have a nuclear membrane."
This statement is incorrect. Prokaryotic organisms (such as bacteria and archaea) lack a membrane-bound nucleus and a nuclear membrane. Their genetic material is suspended directly in the cytoplasm. Only eukaryotic organisms have a well-defined nuclear membrane surrounding their genetic material.

Statement D: "All have a cell membrane."
This statement is correct. The cell membrane (also known as the plasma membrane) is a fundamental structure present in all living cells (both prokaryotes and eukaryotes). It forms the outer boundary of the cell, separating the internal cellular environment from the external surroundings and regulating the movement of substances in and out of the cell.

Therefore, only statement D is correct.