Final answer:
Option (C), Striations are the unique microscopic markings on a bullet caused by the lands and grooves of a gun's barrel, which can be used to trace the projectile back to a specific weapon.
Step-by-step explanation:
The unique markings on a bullet or projectile that can be traced back to a specific weapon are called striations. These striations are created when a bullet is fired from a gun and passes through the barrel, making contact with the lands (the raised portions) and grooves (the indentations) that are present in the rifling of the barrel.
Every gun's barrel has a unique pattern of these lands and grooves, which impart a spin on the bullet, stabilizing it in flight, and these microscopic scratches on the bullet match the unique pattern of the barrel from which it was fired.