Geologists collect and study hand samples because they can be used to understand

which

Geologists use a lot of tools to aid their studies. Some of the most common tools used are compasses, rock hammers, hand lenses, and field books.

the cellphone, they would then know if the killer would have contacted them or always hated them. or if it was a breakup. but if that is not the case, then it would be the clothing. to put in a bullet, it would have to be put in by hands. hands have finger prints which, would have giving you the answer of who done it.

explanation:

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.