Final answer:
RNA polymerase I is the enzyme found in the nucleolus responsible for transcribing and processing rRNA and assembling it into ribosomes.
Step-by-step explanation:
RNA polymerase I is the enzyme found in the nucleolus that is responsible for transcribing and processing rRNA and assembling it into ribosomes.
The nucleolus is a specialized nuclear substructure where ribosomal RNA is synthesized, processed, and assembled into ribosomes.
RNA polymerase I synthesizes the different components of the rRNA, which are essential for the process of translation.