Whether it is a fossil fuel or a biofuel, the fuel you put into your car must be burned to release energy that can power the car. This reaction is called combustion, and the engine in your car is an example of an internal combustion engine.

Let's examine a simple combustion reaction so that you can see how energy is released. In the reaction below, methane (the fuel) is burned with oxygen to produce carbon dioxide and water.

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.