To determine the glucose concentration in an unknown solution, equal amounts of several glucose solutions with known concentrations were each combined with the same excess volume of Benedict’s solution. Once mixed, the samples were kept in a thermostatically controlled water-bath at $90\,^{\circ}\text{C}$ for three minutes. The unknown solution was then handled in the same way, 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
- Dvolume of glucose solutions