The correct answer is: A. Nucleolus
Ribosomes are produced in the nucleolus, a small, dense region within the nucleus of a eukaryotic cell. The nucleolus is responsible for the production of ribosomes, which are the organelles that are responsible for protein synthesis. Ribosomes are made up of two subunits, a large subunit and a small subunit. The large subunit is made up of 54 different proteins and 4 ribosomal RNA molecules, while the small subunit is made up of 33 different proteins and 1 ribosomal RNA molecule. The two subunits come together to form a functional ribosome, which is able to translate messenger RNA into proteins.
Plasmids are small, circular DNA molecules that are found in bacteria and some other prokaryotic cells. Plasmids are not essential for the survival of the cell, but they can confer certain advantages, such as antibiotic resistance or the ability to produce toxins. Plasmids are not produced in the nucleolus.
Mitochondria are organelles that are found in eukaryotic cells. Mitochondria are responsible for the production of ATP, which is the energy currency of the cell. Mitochondria are not produced in the nucleolus.
Therefore, the correct answer is: A. Nucleolus