Question

in the elongation stage of translation,

rrna is catalytically active.

trna is catalytically active.

peptidyl transferase activity is catalyzed by a ribosomal protein.

the polypeptide chain grows from the c terminus to the n terminus.

the message is read in a 3-to-5 direction.

Explanation:

In translation elongation, the peptidyl transferase activity (forming peptide bonds) is catalyzed by the 23S rRNA (a ribozyme) in the large ribosomal subunit, not a protein. rRNA has catalytic activity here. tRNA carries amino acids but is not catalytic. The polypeptide chain grows N-terminus to C-terminus, and mRNA is read 5'-to-3'.

Answer:

A. rRNA is catalytically active.