The correct option is C in vitro replication of specific DNA sequence using thermostable DNA polymerase
Polymerase Chain Reaction (PCR) is a technique which was developed by Kary Mullis in 1985. It is used for in vitro replication of specific DNA sequence using thermostable DNA polymerase.
In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
Studies that are in vivo are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and plants and PCR is not conducted under in vivo conditions.
Gel electrophoresis is a technique used for the separation of DNA fragments according to their size.
The in vivo synthesis of mRNA is the process of transcription, that occurs in various organisms.
The polymerase chain reaction cannot be used for the synthesis of mRNA. The PCR process is used to amplify short segments of a DNA molecule.