Which one of the following is not found in animal cells ?

Which one of the following is not found in animal cells ?

Free ribosomes
Mitochondria
Nucleolus
Cell wall
This question was previously asked in
UPSC CDS-2 – 2019
Animal cells and plant cells share many common organelles like the nucleus, mitochondria, ribosomes, endoplasmic reticulum, and Golgi apparatus. However, there are key structural differences.
A cell wall is a rigid outer layer that provides structural support and protection to the cell. It is a characteristic feature of plant cells (made primarily of cellulose), fungi, algae, and bacteria, but it is *not* found in animal cells. Animal cells are enclosed only by a cell membrane.
Free ribosomes (involved in protein synthesis) are found in the cytoplasm of both animal and plant cells. Mitochondria (responsible for cellular respiration) are present in both. The nucleolus (involved in ribosome synthesis) is located within the nucleus of both animal and plant cells.