Which of the following functionally competent of largest unit of the ribosomes?

Ribosomes catalyze peptide bond formation between aminoacyl- tRNA (aa-tRNA)4 bound to the A site of the ribosome and peptidyl- tRNA at the P site.The active site for peptide bond formation, the peptidyl transferase center, is located on the large (50 S) ribosomal subunit. High-resolution crystal structures of the 50 S subunit have revealed that the peptidyl transferase center is composed of RNA (23 S rRNA), with no protein within 15 A of the active site (1, 2).This implies that peptide bond formation is catalyzed by RNA and, thus, the ribosome is a ribozyme.