Le Chatelier's principle applied to equilibrium shift

Steps:

• Identify the reaction as exothermic (ΔH negative), so decreasing temperature favors products.
• Count moles of gas: 9 on reactants, 10 on products, so increasing pressure favors reactants.
• Catalyst affects rate, not position.
• Option D (unspecified) must be the perturbation that shifts toward more NO.

Not enough information: Option D is blank, so cannot confirm what increases [NO].

Why D is correct:

• Insufficient details provided for D.

Why the others are wrong:

• A: Decreasing temperature shifts exothermic reaction right, increasing [NO].
• B: Catalyst speeds attainment of equilibrium but does not shift position.
• C: Increasing pressure favors side with fewer gas moles (reactants), decreasing [NO].

Final answer: Not enough information.