The correct option is D 4
The four nitrogenous bases found in mRNA are adenine (A), guanine (G), cytosine (C) and uracil (U).
A set of three nucleotides present on mRNA that encodes information for a particular amino acid is called codon. The genetic code is degenerate which means more than one codon encodes for the same amino acid. Therefore there are 64 triplet codons coding for 20 amino acids.
The triplet codons made up of the same bases in the 64 triplet codons are AAA, GGG, UUU, CCC coding for amino acids lysine, glycine, phenylalanine and proline respectively.