Correct answer is (d) Transcription
The best I can explain: The diagram represents the process of site directed mutagenesis which starts with deprival of primary structure of the enzyme from the DNA sequence. Primary structure of putative enzyme is proposed with replacing another aminoacid present in the native enzyme. This is followed by synthesis of primer which is complementary to a section of the gene apart from the base mismatch. The oligonucleotide primer is then annealed to a single-stranded copy of the gene and polymerase chain reaction occurs which produces both mutant and wild-type clones. Finally, the mutant DNA is identified by hybridization with radioactively labelled oligonucleotides.