You are answering a USMLE-style medical question. Question: A 27-year-old HIV positive female gave birth to a 7lb 2oz (3.2 kg) baby girl. The obstetrician is worried that the child may have been infected due to the mother's haphazard use of her anti-retroviral medications. Which of the following assays would a hospital use detect the genetic material of HIV if the child had been infected? Options: A) Enzyme-linked immunosorbent assay (ELISA) B) Rapid HIV antibody test C) Polymerase chain reaction D) Southern blot Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.