Explanation

The organelle that is not present in animal cells is the Plastid. 

Plastids, including chloroplasts, are organelles specific to plant cells and are not found in animal cells. 

Endoplasmic Reticulum:

Present in both animal and plant cells. 

Ribosome:

Present in all cells, as they are the site of protein synthesis. 

Mitochondria:

Present in most animal cells, responsible for generating energy.