Which of the following is NOT a characteristic exhibited by aminoacyl-tRNA synthetases?

A)Some are monomeric and others are oligomeric.
B)They attach the amino acid to the 2'- or the 3'-hydroxyl of the ribose located at the 5'-end of the tRNA.
C)They attach the amino acid to a terminal adenylate residue on the tRNA.
D)Through binding specificity,they relate specific amino acids to appropriate codons.