The correct answer is option 3: 3 moles of H2(g) are required to saturate one mole of benzene.

To understand why 3 moles is the correct answer, we need to consider the chemical reaction that occurs when benzene is saturated with hydrogen gas (H2). The reaction, known as hydrogenation, involves the addition of hydrogen to the benzene molecule.

The balanced chemical equation for the hydrogenation of benzene is:

C6H6 + 3H2 [REPLACEMENT] C6H12

From the balanced equation, we can see that each benzene molecule (C6H6) reacts with 3 hydrogen molecules (H2) to produce one molecule of cyclohexane (C6H12), which is the saturated form of benzene.

Since the question asks for the number of moles of H2 required to saturate one mole of benzene, we can conclude that 3 moles of H2 are needed. This is because the balanced equation shows that the mole ratio between benzene and hydrogen is 1:3.

Therefore, option 3: 3 moles is the correct answer.