Which of the following is the site for synthesis of ribosomal ribonucleic acid (rRNA)?

The correct answer is the nucleolus, which plays a crucial role in the synthesis of ribosomal ribonucleic acid (rRNA). The nucleolus is a specialized structure within the nucleus where rRNA is transcribed, processed, and assembled into ribosomal subunits. This process is vital for the formation of ribosomes, which are essential for protein synthesis in the cell.

While the nucleus contains the overall genetic material and is where transcription occurs, it is the nucleolus specifically that is dedicated to rRNA production. Ribosomes themselves are the sites of protein synthesis but are not involved in the synthesis of rRNA. The cytoplasm is where ribosomes function in translation but does not facilitate the production of rRNA. Hence, the nucleus is important, but the nucleolus is the specific site for rRNA synthesis.