Answer:
c. Some codons specify the same amino acid.
Explanation:
Codons are triplets of nucleotides in mRNA that is used for the protein synthesis (translation). A codon specifies a single amino acid, but there are exceptions. tRNA molecule contain anticodons, triplets of nucleotides that are complementary to codons. So, during the translation, tRNA carries the amino acid, that corresponds to  the codon in mRNA.