Correct Answer - C
`SnCI_(4)` is a Lewis acid because the tin atom can expend its valence shell by utilizing vacant d-orbitals. All positively charged ions are not Lewis bases, e.g., `Cu^(2+)` and `Ag^(+)` ions cannot act as Lewis bases but not Lewis acids, e.g., `CI^(-)` and `CN^(-)` ions. A species in which the central atom has complete octet can act as an acid provided it is `pi`-bonded to highly electronegative atom, e.g., `CO_(2)`.
