Which structure is usually present only in animal cells?
Vacuoles are storage bubbles found in animal and plant cells, but bigger in plant cells. These are used for the storage of food or water.
The cell wall is a protective outer covering of the cell. It is mostly present in plant cells. It supports the contents of the cell and protects from pathogen attack and wear and tear. It is made of cellulose, lignin.
The nucleus of the cell contains a majority of the cell's genetic material, i.e., DNA in the form of a DNA-protein complex, called chromatin. It is present in both animal and plant cells.
Animal cells contain centrioles, cylindrical organelles that help in cell division and are absent in plant cells. Thus, the correct answer is option D.