• According to Gay-Lussac's Law, for a fixed mass of gas at constant volume, the absolute pressure varies directly with the absolute temperature. 
• This means that as the temperature of the gas increases, the pressure also increases proportionally, and vice versa.
• Mathematically, this is expressed as P/T = constant, or P₁/T₁ = P₂/T₂. 

Hence, the correct option is (C).