Which technique generates multiple copies of the DNA?

The correct answer is Option (2) → Polymerase Chain Reaction

Option (2) Polymerase Chain Reaction — Correct. PCR (Polymerase Chain Reaction) makes multiple copies of a chosen piece of DNA in vitro, using two primers and a heat-stable DNA polymerase; repeating the cycle can give about a billion copies.

NCERT Extract:
Amplification of Gene of Interest Using PCR – “… PCR stands for Polymerase Chain Reaction. In this reaction, multiple copies of the gene (or DNA) of interest is synthesised in vitro using two sets of primers (small chemically synthesised oligonucleotides that are complementary to the regions of DNA) and the enzyme DNA polymerase. The enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as template. If the process of replication of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times, i.e., 1 billion copies are made.”