To estimate the amount of glucose in a solution, the same volumes of a set of solutions with known concentrations were each combined with the same excess volumes of Benedict’s solution and then kept in a thermostatically controlled water-bath at $90^\circ\text{C}$ for an identical period of time. After that, the unknown solution was treated in exactly the same manner, and the colours of the known and unknown solutions were compared. What is the independent variable in this procedure?
- Aconcentration of glucose
- Bfinal colour of solutions
- Ctemperature of water-bath
- Dvolumes of glucose solutions