Which one of the following enzymes is obtained from Thermophilus aquaticus bacterium which is heat stable and use in PCR at high temperature?

Reverse Transcriptase PCR (-PCR) It is the method used to amplify, isolate or identify a known sequence from a cell or tissue RNA library. Essentially normal PCR is preceded by reverse transcription (to conve the RNA to cDNA). This is widely used in expression mapping, determining when and where ceain genes are expressed. Instead of Taq polymerase described above, Tth polymerase from Thermus thermophilus may be used. This enzyme has both DNA polymerase and reverse transcriptase activities at high temperature. This allows both cDNA synthesis from mRNA followed by PCR amplification. In ordinary PCR, DNA is detected; that DNA could be from a living or non-living organism. But in reverse PCR, mRNA is detected; that means, it is derived from a living organism. Presence of HIV RNA in the blood can be detected as early as 4 weeks after infection.Ref: DM Vasudevan, page no: 618