Where are ribosomes primarily made within the cell?

Ribosomes are primarily made in the nucleolus, which is a dense region found within the nucleus of eukaryotic cells. The nucleolus is responsible for synthesizing ribosomal RNA (rRNA) and combining it with proteins to form the subunits of ribosomes. Once these subunits are assembled, they can either remain in the nucleus or be transported to the cytoplasm, where they play a crucial role in protein synthesis.

The other options do not accurately describe the primary location of ribosome assembly. The cell membrane is involved in interactions with ribosomes and protein synthesis but is not where ribosomes are formed. The nucleus contains the nucleolus but is not the direct site of ribosome production; the nucleolus is the specific structure within it. Lastly, while ribosomes function in the cytoplasm, they are not made there; rather, they are synthesized in the nucleolus before moving to the cytoplasm for their role in translating mRNA into proteins.