Answer:
3-2-1
Step-by-step explanation:
PCR is the process of DNA duplication in vitro. We can make millions of copies of DNA in a very short period.
PCR completed in three steps; as in question these are
Step 1: Denaturation; Heat separation of strands of target DNA.
Step 2: Annealing; as complementary base pairing between primers and target DNA.
Step 3: Extension; Addition of DNA nucleotides by Taq DNA polymerase.