• relative humidity decreases
• Brelative humidity increases
• Cspecific humidity increases
• Dspecific humidity decreases

In a closed (sealed) metallic vessel, no water vapor can enter or leave, so the mass of vapor per unit mass of dry air (specific humidity) stays constant. But heating raises the saturation pressure of water at the higher temperature, so the same vapor content represents a smaller fraction of the increased saturation capacity — relative humidity decreases.