Arolling ball will eventually stop rolling. which describes one reason why this happens

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

if it's not useful, feel free to report for mistake in answer.

a corroding iron, if that's one of your choices

you need to have a picture of the atom that way we can answer it

it is b that is the answer.