Answer- A. CRISPRA type of genetic engineering in which DNA is inseed, deleted or replaced in the genome of a living organism using engineered nucleases, or "molecular scissors.Four Families of Engineered Nucleases being usedMeganucleasesTranscription Activator-Like Effector-based Nucleases (TALEN)Zinc finger nucleases (ZFNs)Clustered Regularly Interspaced Sho Palindromic Repeats (CRISPR)-Cas systemForm the basis of a genome editing technology known as CRISPR/Cas9 that allows permanent modification of genes within organisms.