PCR Involves a Heating Step, Followed by a Cooling Step

PCR involves a heating step, followed by a cooling step, and then DNA synthesis.What is the primary reason for why this cooling step is necessary?

A) Cooling the reaction ensures the integrity of the covalent bonds holding the nucleotides together in the DNA strand.
B) Cooling the reaction gives the DNA polymerase an opportunity to rest from the previous cycle so that it will be ready for the next round of synthesis.
C) Transcription takes place during the cooling step.
D) Cooling the reaction brings the temperature down to a level that is compatible with the short primers forming stable hydrogen bonds with the DNA to be amplified.