The Polymerase Chain Reaction (PCR) Technique Could Be Developed Only

The polymerase chain reaction (PCR) technique could be developed only after the discovery of bacterial enzymes that were able to withstand high temperatures. Why was it necessary to use such enzymes?

A) Only bacterial DNA can be copied using the PCR method, so bacterial enzymes were necessary.
B) Bacterial enzymes can only move through the gel during PCR electrophoresis.
C) DNA can only be cut into fragments at high temperatures.
D) The temperature required to separate DNA strands during PCR degrades most normal enzymes.