A significant part of ballistics involves examining used:
a. small, round pellets for telltale markings left on them by the firearm that shot them.
b. gunpowder for telltale markings left on it by the firearm that shot it.
c. bullets and their spent cartridge casings for telltale markings left on them by the firearm that shot them.
d. shot for telltale markings left on them by the firearm that shot them.