Derive the relationship between pressure and volume of gas at a constant temperature using Charles's law and Gay-Lussac's law.

• A. P₁/V₁ = P₂/V₂
• B. P₁/V₂ = P₂/V₂
• C. P₁V₁ = P₂V₂
• D. P₁/V₂ = P₂/V₁

Answer: (C)