(b) : Genetic code is non­ambiguous. Non­ ambiguous code means that there is no ambiguity about a particular code. One codon specifies only one amino acid and not any other. There are $64$ codons. Out of $64, 3$ are stop codons or nonsense codons, $i.e.$, these do not code for any amino acid and rest $61$ code for one of the $20$ amino acids. Neither of them code for more than one amino acids except $GUG$ which normally code for valine but in certain conditions it also codes for N­formyl methionine as initiation codon.