According to what is known about chemical equilibrium and Le Chatelier's principle, when you increase the amount of the reactants, the reaction will be moved to the products, this is because, the most reactants we have the most products we can produce.
From the given choices, the one that goes according to this reason is the third one: The volume of water vapor increases.
The answer is A because it cannot be B because that is ethylene and not D because it needs a subscript of 2 since it is a diatomic and it is no C because it is not carbon dioxide its oxygen
