What is the primary role of RNA Pol I, II, and III in eukaryotic cells?

The primary role of RNA polymerases I, II, and III in eukaryotic cells is indeed to transcribe different types of RNA, making option A the correct answer. Each RNA polymerase has a specific function:

• RNA polymerase I is primarily responsible for synthesizing ribosomal RNA (rRNA), which is essential for the assembly of ribosomes, the cellular machinery that translates mRNA into proteins.

• RNA polymerase II synthesizes messenger RNA (mRNA), which carries the genetic information from DNA to the ribosome for protein synthesis. It also produces small nuclear RNAs (snRNAs) that are involved in splicing and other RNA processing activities.

• RNA polymerase III has the role of transcribing transfer RNA (tRNA), which serves as the adaptor molecule in protein synthesis, as well as other small RNAs, including some types of rRNA.

These roles emphasize the integral part that each RNA polymerase plays in the flow of genetic information from DNA to RNA, which is crucial for gene expression and cellular function. Therefore, the answer highlights the distinct and essential roles of RNA polymerases in the transcription process within eukaryotic cells.