Why does a liquid’s surface tension decrease with increasing temperature?
Increasing temperature weakens cohesive forces between liquid molecules by increasing their kinetic energy, reducing the contractile force at the surface, thus lowering surface tension, as noted in the chapter. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Cohesive forces weaken. This satisfies dimensional consistency and physical conditions given, so option C is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.