The correct option is A AlCl3⋅6H2O
Lewis acid : Species which can accept an electron pair using an empty orbital of right energy with the formation of a coordinate bond.
AlCl3 acts as a Lewis acid as central atom Al has incomplete octet or empty orbitals. SnCl4 and FeCl3 act as Lewis acid because Sn and Fe both have vacant d-orbitals.
AlCl3 is sp2 - hybridised, i.e., it has vacant one 3 p-orbital and five 3d-orbitals. So, central atom has also the ability to accept lone pairs in their empty orbitals.
But in AlCl3⋅6H2O one vacant 3p-orbital and five vacant 3d-orbitals are filled by the electron pair oxygen. So AlCl3⋅6H2O cannot act as a Lewis acid.