Questions: Which phrase correctly identifies the role of rRNA? A. Transcribing DNA into RNA polymerase to start protein formation B. Working with ribosomal proteins and tRNA to make a polypeptide C. Carrying the genetic code from DNA to the cytoplasm for translation D. Carrying amino acids to the site of protein synthesis

The answer is B: Working with ribosomal proteins and tRNA to make a polypeptide.

Explanation for each option:

A. Transcribing DNA into RNA polymerase to start protein formation - This is incorrect. Transcription is the process where DNA is transcribed into mRNA, not rRNA. RNA polymerase is the enzyme that facilitates this process, but rRNA is not involved in transcription.

B. Working with ribosomal proteins and tRNA to make a polypeptide - This is correct. rRNA (ribosomal RNA) is a key component of ribosomes, which are the cellular structures where protein synthesis occurs. rRNA helps to catalyze the formation of peptide bonds between amino acids, working alongside ribosomal proteins and tRNA during translation to form polypeptides.

C. Carrying the genetic code from DNA to the cytoplasm for translation - This is incorrect. This is the role of mRNA (messenger RNA), not rRNA. mRNA carries the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm.

D. Carrying amino acids to the site of protein synthesis - This is incorrect. This is the role of tRNA (transfer RNA), which transports amino acids to the ribosome during protein synthesis.

In summary, rRNA's role is to work with ribosomal proteins and tRNA to facilitate the synthesis of polypeptides, making option B the correct choice.