At the start of the universe, there was just very hot, small particles mixed with light and energy. As these particles cooled, they started to take up more space. These particles started to group together, like rolling a snowball. Over a long period of time, these groups of particles would form stars and galaxies. What other features in space appear as stars are formed or die?

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.