The correct option is A
Statements (I) and (II) are correct, but statement (III) is incorrect
RT-PCR (Reverse transcription-polymerase chain reaction) is a highly sensitive technique which is used for detection and quantification of RNA.
PCR or polymerase chain reaction is a technique used in molecular biology to create several copies of a certain DNA segment. PCR does not work on RNA directly. Hence in RT-PCR, the RNA is reverse transcribed into complementary DNA (cDNA), using reverse transcriptase, and then PCR is used to amplify the cDNA.
Statement I is correct: RT-PCR is a variation of PCR with an additional step of reverse transcription. Coronavirus contains RNA as genetic material and is responsible for Covid-19, hence RT-PCR is used for performing its identification test.
Statement II is correct: Pathogens such as HIV (Human Immunodeficiency Virus) have RNA as their genetic material like coronavirus. Hence RT-PCR can be used to detect HIV.
Statement III is incorrect: Most of the infections caused by retrovirus (virus containing RNA as genetic material) are tested using RT-PCR. For eg: In case of testing for coronavirus, samples obtained from a patient's nose and throat swabs containing active virus are used. The viral RNA is reverse transcribed to cDNA using reverse transcriptase, followed by PCR which is used to amplify the cDNA. Hence the test works by isolating the RNA sequence in the virus and not the antibodies produced against it. For antibody detection, ELISA can be used.