The correct option is D a thermophilic bacterium
Thermus aquaticus is a thermophilic bacterial species, an extremophile. It can survive in hot springs with temperature range of upto 50−80°C.
The species can replicate its genetic material with the help of heat resistant enzyme Taq DNA polymerase.
Polymerase chain reaction (PCR) is the process of selective amplification of a specific region of DNA in vitro. For the amplification of the desired copy of the DNA by the process of polymerase chain reaction (PCR), it needs a very high thermostable polymerase to perform its function even in fluctuating temperatures inside the thermocycler, which is why Taq polymerase is used in PCR.