The answer would be bone marrow
The most appropriate answer is A !!
RFLP or Restriction Fragment Length Polymorphism exploits the variation of homologous DNA (Deoxyribonucleic Acid) sequences. This technique is frequently used in different types of analysis such as genotyping, paternity tests, forensics, hereditary disease diagnostics, and many others. In diagnosing diseases, PCR is use to find the DNA of pathogens in small amounts to diagnose hundreds of genetic diseases. While in forensic investigations, PCR can give a probably ID from 20 cells.