The right answer is eight.
PCR (polymerase chain reaction) is a method of molecular biology of in vitro gene amplification. It makes it possible to duplicate in large numbers (with a multiplication factor of the order of one billion) a known DNA or RNA sequence, from a small quantity (of the order of a few picograms) of acid. nucleic acid (specific DNA sequence (Amplicon)) and specific primers consisting of synthetic oligonucleotides of 20 to 25 nucleotides.
So, from a DNA molecule, we get 2 molecules in the first cycle, then 4 in the second cycle, and finally 8 in the third cycle.