The correct answer is option 2: two volumes of ammonia.

In this chemical reaction, one volume of nitrogen combines with three volumes of hydrogen to produce two volumes of ammonia. This is known as the Haber process, which is used to commercially produce ammonia.

To understand why two volumes of ammonia are produced, we need to look at the balanced chemical equation for this reaction:

N2 + 3H2 --> 2NH3

The equation tells us that one molecule of nitrogen (N2) reacts with three molecules of hydrogen (H2) to form two molecules of ammonia (NH3). Since the number of molecules can be directly related to volumes, we can say that one volume of nitrogen combines with three volumes of hydrogen to produce two volumes of ammonia.

It`s important to note that the balanced chemical equation shows the mole ratio of each substance involved in the reaction. It informs us about the relative amounts of reactants and products and allows us to determine the stoichiometry of the reaction.