Assertion: square planar $[\mathrm{Pt}(\mathrm{NH}{}_3)(\mathrm{py})\mathrm{ClBr}]$ has four different ligands and therefore must exist as pairs of optical isomers. Reason: a square planar complex with four different ligands still has the molecular plane as a plane of symmetry.

1. ABoth Assertion and Reason are true and the Reason is the correct explanation of the Assertion
2. BBoth Assertion and Reason are true but the Reason is not the correct explanation of the Assertion
3. CAssertion is true but Reason is false
4. DAssertion is false but Reason is true