If 8 molecules of CO and 5 molecules of O₂ react to form CO₂, what is the limiting reactant, and how many molecules of the excess reactant will remain when the reaction is complete?

a) CO is the limiting reactant, 3 molecules of O₂ remain.
b) O₂ is the limiting reactant, 3 molecules of CO remain.
c) CO is the limiting reactant, 2 molecules of O₂ remain.
d) O₂ is the limiting reactant, 2 molecules of CO remain.