The answer is C) the weight of the flour.
The only thing you can measure with a scale is the weight of an object, not the colour, not the temperature, neither the volume.
Volume = length x width x height.
Temperature is the quantity measured by a thermometer.
Colours are derived by the amount of energy present at each spectral wavelength.
Weight is commonly measured using one of two methods. A spring scale or hydraulic or pneumatic scale measures local weight, the local force of gravity on the object (strictly apparent weight force).