Correct Option: A

Real-time quantitative reverse transcriptase–polymerase chain reaction (RT–PCR) is the method of choice for rapid and reproducible measurements of cytokine or growth factor expression in small samples. Fluorescence detection methods for monitoring real-time PCR include fluorogenic probes labelled with reporter and quencher dyes, such as Taqman probes or Molecular Beacons and the dsDNA-binding dye SYBR Green I. ​​
SYBR Green binds to the minor groove of the dsDNA only. In the solution the unbound dye exhibits little fluorescence. This fluorescence is enhanced when the dsDNA is bound with dye. ​