The correct option is D Ribosome
The nucleolus is naked roughly rounded darkly stained structure that is attached to chromatin at a specific spot called Nucleolar Organiser Region or NOR. Nucleolus contains four parts- Amorphous, Fibrillar, Granular and Chromatin. Both fibrillar and granular parts are formed of RNA and proteins. The nucleolus is the site for the elaboration of rRNA and synthesis of ribosomes. It is, therefore, called Ribosomal Factory. Ribosomal protein is synthesized in the cytoplasm.