In reviewing evidence from a cold case, Investigator Chang realizes that the original investigators did not collect any DNA evidence. She's found a possible blood spot on some clothing in evidence that could yield some DNA of the perpetrator. She also knows that the investigators had a suspect in mind but could never prove her involvement. However, the suspect was embalmed and buried five years ago. Why will Investigator Chang be unable to collect DNA from the suspect?

DNA is no longer available after three years.
An embalmed body isn't suitable for DNA testing.
A body that has been buried in dirt corrupts DNA material.
DNA testing techniques can't extract DNA from dead bodies.