What method could be used to measure the quantity of reducing sugar in a solution?

To measure the quantity of reducing sugars in a solution accurately, the correct method involves filtering and drying the precipitate. This method is associated with precipitation reactions, where reducing sugars can be reacted with specific reagents (like Benedict's solution) to form an insoluble complex, resulting in a precipitate.

When you filter the solution, the solid precipitate that forms can be collected and dried to remove any moisture. The mass of this dried precipitate can then be weighed. The amount of precipitate formed is directly related to the concentration of the reducing sugar in the original solution, allowing for quantitative analysis.

In contrast, directly mixing with starch solution would not yield useful information about reducing sugars, as starch is not a reducing sugar and does not form a colored reaction with it. Measuring the pH of the solution does not quantify reducing sugars, as various factors can affect pH unrelated to sugar content. Using a digital thermometer measures temperature, which is not indicative of sugar concentration and does not provide useful data regarding reducing sugars.