What structure is present only in animal cells that plays a role in cell division?

The centriole is a cylindrical structure that plays a critical role in cell division, particularly during the process of mitosis and meiosis in animal cells. Centrioles are involved in the formation of the mitotic spindle, which helps to separate chromosomes into the daughter cells during cell division. They are usually found in pairs and are located in the centrosome, which is the main organizing center for microtubules in the cell.

While chloroplasts are found in plant cells and are responsible for photosynthesis, and the cell wall is also unique to plant cells, providing structural support, and the nucleus is present in both plant and animal cells, it is the centriole that is specifically associated with the processes of division in animal cells. This makes the centriole unique in its role as it is not present in plant cells, further distinguishing the functions of different cellular structures in eukaryotic organisms. Thus, the correct answer highlights the specific function and exclusive presence of centrioles in animal cells during the crucial process of cell division.