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:

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of carbon is as shown here in the image.