Which of the following acts as a Lewis acid in the following reaction ${\mathrm{SnCl}}_4+2{\mathrm{Cl}}^{-}\to {\left[{\mathrm{SnCl}}_6\right]}^{-2}$ ?

• A

  Cl^-

• B

  [SnCl₆]^2-

• C

  SnCl₄

• D

  2Cl^-