Because, when an infection exist in the human body it tends to spread, so if the cells stayed in one space then the infection would have a much greater opportunity to severly make that person very ill before the cells could even get to the infection.
The answer is D because when you get a head injury your most likely to have a concussion from the impact which will cause you to loss consciousness and have blurred vision and dizziness.
The most interesting aspect of working with firearm evidence is finding out which type of firearm was used and inspecting the bullet and matching it to the archives of guns and bullets. However, the challenging part is tracing which person used the firearm and evidence and is the suspect of a crime. Also, tracing the movement of the bullet used from where it was shot and where it landed. It's very hard to know which person used the firearm as the end user.
