For a reaction to be in equilibrium * A. concentration of reactants and products remain constant
B. concentration of reactants and products must be the same
C. the rate of forward reaction is not equal to the rate of backward reaction.

C) the rate of forward reaction is not equal to the rate of backward reaction. This should be the answer.

Explanation:

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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