PLEASE HELP! IM BEING TIMED! Which reaction is exothermic?

CH4 + 2O2 Right arrow. CO2 + 2H2O + 891 kJ
NH4NO3 + H2O + 25 kJ Right arrow. NH4+(aq) + NO3-(aq)
2H2O + 286 kJ Right arrow. 2H2 + O2
N2 + O2 + 181 kJ Right arrow. 2NO

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.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.