Define reversible reaction.

• A. A reversible reaction involves two reactions: the forward reaction, in which all reactants are converted to products, and the reverse reaction, occurring after the forward reaction, in which all products are converted back to reactants.
• B. A reversible reaction involves two reactions: the forward reaction, in which all products are converted to reactants, and the reverse reaction, occurring after the forward reaction, in which all reactants are converted back to products.
• C. A reversible reaction involves two simultaneous reactions: the forward reaction, in which the products are converted to reactants, and the reverse reaction, in which the reactants are converted to products.
• D. A reversible reaction involves two simultaneous reactions: the forward reaction, in which the reactants are converted to products, and the reverse reaction, in which the products are converted to reactants.

Answer: (D)