Identify what Fehling's reagent tests for

Fehling's reagent gives a reddish-brown precipitate of cuprous oxide, $\mathrm{Cu_2O}$, with reducing sugars.

So, we need the sugar that is non-reducing.

Check each option

A. Glucose

• Glucose is an aldose.
• It has a free aldehydic form in equilibrium in solution.
• Therefore, it is a reducing sugar and gives Fehling's test.

B. Sucrose

• Sucrose is formed from glucose and fructose.
• In sucrose, the glycosidic bond involves the anomeric carbon of glucose and the anomeric carbon of fructose.
• Hence, there is no free hemiacetal/hemiketal group available.
• Therefore, sucrose is a non-reducing sugar and does not give Fehling's test.

C. Lactose

• Lactose has one free anomeric carbon.
• Hence it is a reducing sugar.
• It gives Fehling's test.

D. Maltose

• Maltose also has one free anomeric carbon.
• Hence it is a reducing sugar.
• It gives Fehling's test.

Conclusion

The sugar which does not give a reddish-brown precipitate with Fehling's reagent is:

$\boxed{\text{Sucrose}}$

Comparison with stored correct answer

Stored correct answer: B

Derived answer: B (Sucrose)

So, the derived answer matches the stored correct answer.