The correct option is B Exonuclease
Genetic engineering procedures require various molecular tools such as restriction endonucleases, ligases, reverse transcriptases, vectors and markers. Restriction exonucleases are enzymes that cleave nucleotides from the end of a polynucleotide chain. These enzymes do not have a specific cut site or recognition sequence, hence are not used in normal genetic engineering procedures as they require high specificity.