H2 h2o h2o2 ch4 all four examples represent

molecules

Justification:

1) Given formulas: H₂, H₂O, H₂O₂, CH₄.

2) A molecule is the chemical combination of two or more atoms through covalent bonds.

3) Non-metals only can bond among them by covalent bond, i.e. by sharing electrons.

Two nonmetals cannot bond to each other in other way (ionic bonds) because any of them will not be willing to release an electron completely.

Since the two nonmetal elements just need a few more electrons to complete their respective valence electron shell, they will do it by sharing electrons instead of releasing them.

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 electronegativity decreases beacuse the size of nucleus is bigger.