In the genetic code,
a) some amino acids are not specified by any codons
b) many amino acids are specified by more than one codon
c) some codons consist of two nucleotides
d) some codons specify more than one amino acid

Option b) many amino acids are specified by more than one codon

Explanation:

The degenerate nature of the genetic code permits that more than one codon specify for an amino acid. Thus, the 64 codons present in nature can justifiably specify for the standard 20 amino acids.

For instance: the codons GGU, GGC, GGA and GGG all code for the amino acid, Glycine.

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