The correct option is C Polymerase chain reaction
Thermocyclers, or thermal cyclers, are instruments used to amplify DNA and RNA samples by the polymerase chain reaction. The thermocycler raises and lowers the temperature of the samples in a holding block in discrete, pre-programmed steps, allowing for denaturation and reannealing of samples with various reagents. Amplified genetic material can be used in many downstream applications such as cloning, sequencing, expression analysis and genotyping.