Answer:
Option C; NONE.
Step-by-step explanation:
A chemical reaction forms new chemicals called the products from the initial chemicals called the reactants. The reaction between an acid and a base is called neutralization, and the products formed are water and a salt.
When hydrochloric acid and sodium hydroxide is mixed together, they interact, and result in salt and a release of heat.
The result of the interaction of these two highly aggressive compounds is table salt and water, these resulting compounds are ultimately harmless, and even beneficial, to human beings.
Therefore, NO TOXIC GAS WOULD BE FORMED BY MIXING HYDROCHLORIC ACID WITH SODIUM HYDROXIDE.