Classify the items based on whether they are or are not matter.

Matter:

toothpaste

gasoline

bacteria

cell

Not matter:

happiness

sound

Explanation:

Matter is something that has mass and volume. Happiness is just a feeling, it doesn't exist in 3d world. Sound is a wave or just the movement of matter (particles of matter). Others have masses and volumes.

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.

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