1. Identify the product complex $A$

   Ferric chloride reacts with oxalic acid / oxalate in presence of base to form the ferrioxalate complex.

   Oxalic acid gives oxalate ion $\mathrm{C_2O_4^{2-}}$, which is a bidentate ligand.

   Iron is in the $+3$ oxidation state, so the complex formed is: $[\mathrm{Fe(C_2O_4)_3}]^{3-}$

2. Geometry of the complex

   Since there are three bidentate oxalate ligands, the coordination number is $6$.

   Hence the complex has octahedral geometry.

3. Optical activity check

   The complex is of type: $[M(AA)_3]$ where $AA$ is a symmetrical bidentate ligand.

   Such octahedral complexes exist as two non-superimposable mirror images:

   • $\Delta$
   • $\Lambda$

   Therefore, the complex shows optical isomerism.

4. Count of optical isomers

   For an octahedral complex of type $[M(AA)_3]$, the number of optical isomers is: $2$

So, the iron complex $A$ exhibits 2 optical isomers.