Answer:
The correct answer will be option-nucleus
Explanation:
The living organisms can be classified as prokaryotes and the eukaryotes. They both can be distinguished on the basis of the presence of cellular organelles.
The nucleus which encloses the genetic material of the organism is present only in the eukaryotic organism and not in the prokaryotes like bacteria. Also, the nucleus in multicellular organism is not present in the cells which do not require it based on the functions like red blood cells.
Therefore the nucleus is the organelle which is not present in all cells and is the correct answer.
