DNA Analysis Modern Forensics-Science Used in Investigating Crimes-Relies Heavily on DNA Evidence

DNA analysis
Modern forensics-science used in investigating crimes-relies heavily on DNA evidence. Nearly every cell in our bodies contains DNA, the molecule that carries our genetic information. Aside from identical twins, no two human beings have the exact same DNA. Because DNA is present in our hair, blood, skin, and saliva, we leave traces of our DNA just about everywhere we go. Forensic investigators collect and analyze DNA evidence left at crime scenes to identify criminals.
On television, this process is quick and conclusive. In real life, however, it is much more complicated. If the material found at the crime scene is too small, too old, or has otherwise been damaged, analyzing the DNA can be difficult. Furthermore, if the sample came from teeth, hair, or bones, it must undergo a different type of analysis called mitochondrial DNA analysis, which uses DNA from a cell's mitochondria instead of the nucleus. Matching mitochondrial DNA is often more difficult than nuclear DNA.
Furthermore, forensic experts never suggest that DNA evidence is concrete proof of a suspect's guilt. Forensic science is rooted in probability, not certainty. When the DNA of a suspect is found at a crime scene, it means that the suspect was likely to have been present at the crime scene, but it does not definitively indicate that he or she was guilty of a crime.
Question: What is the main idea of the passage?

A) Most of the cells in our body contain DNA, a molecule that carries genetic information.
B) We leave traces of our DNA just about everywhere we go.
C) DNA is a foolproof tool for assessing the guilt of a criminal suspect.
D) The use of DNA, the molecule that carries genetic information, has some drawbacks.