Answer: The correct answer will be 5 moles, because according to the stoichiometric ratio, 5 moles of oxygen produce 6 moles of water.
Explanation:
The balanced equation is:
[tex]4NH_{3} + 5O_{2}[/tex] ⇒ [tex]4NO + 6H_{2}O[/tex]
As you can see in the balanced reaction, it is necessary 5 moles of oxygen for obtain 6 moles of water. This stoichiometric ratio can be used for calculate any amount of produced water, once you have a specific amount of oxygen.