Perhaps you have noticed the dull, white substance that appears on an aluminum screen door. This substance is aluminum oxide, Al2O3, and it forms from the reaction of aluminum metal, Al, and oxygen, O2. Which of these chemical equations is correct for this reaction? A. Al + O2 → Al2O3
B. 2 Al + O2 → Al2O3
C. 2 Al + 3 O → Al2O3
D. 4 Al + 3 O2 → 2 Al2O3

Okay well gravitational energy is matter forced by gravity making energy though the kinetic energy then the electric energy produces electricity from the kinetic energy and the kinetic energy gets its energy from the gravitational energy. was that the answer you wanted or something else?  

Are there any options that could alot..

Answer is: the equilibrium  shifts toward the reactants, to the left side of chemical reaction.it is because lead(ii) nitrate dissociates in water: pb(no₃)₂ → pb²⁺(aq) + 2no₃⁻(aq).according to lechatelier's principle, the position of equilibrium moves to counteract thechange (more lead cations, common ion), the position of equilibrium will move so that the concentration ofproducts decrease and concentration of reactants of chemical reaction increase.read more on -