1. Identify the ligand in Fehling's reagent

   Fehling's reagent is prepared by mixing:

   • Fehling A: aqueous $\mathrm{CuSO_4}$
   • Fehling B: alkaline sodium potassium tartrate solution

   Therefore, the ligand present in Fehling's reagent is tartrate ion.

2. Write the structure-related coordination sites of tartrate

   Tartrate ion is derived from tartaric acid: $\mathrm{HOOC-CHOH-CHOH-COOH}$

   In alkaline medium, it exists as tartrate ion with deprotonated carboxylate groups. The possible donor atoms are:

   • two oxygen atoms from the two $\mathrm{-COO^-}$ groups
   • two oxygen atoms from the two hydroxyl groups

3. Count the donor atoms

   So tartrate can coordinate through a total of: $2 + 2 = 4$ donor atoms.

4. Denticity

   Hence, tartrate acts as a tetradentate ligand in Fehling's reagent.

Therefore, the denticity is: $\boxed{4}$

5. Comparison with stored answer

   Stored correct answer = $4$

   Our derived answer also = $4$

   So, the derived answer agrees with the stored correct answer.