The Codons with dual functions are
I. AUG  
II. GUG 
III. UAG  
IV. UGG

detailed solution

Correct option is B

The codon AUG can act as initiating codon as well as interstitial codon. As initiating codon, it indicates amino acid methionine in eukaryotes and formyl methionine in prokaryotes. As interstitial codon it indicates methionine in both Prokaryotes and Eukaryotes. GUG acts as initiating codon in some prokaryotic mRNAs and indicates formyl methionine and as subsequent codon it indicates amino acid Valine. It indicates only Valine in Eukaryotes. UAG is non-sense codon and does not indicate any amino acid. UGG indicates only the amino acid Tryptophan.