Which of the following statements is correct ?

• A

  ${\mathrm{BCl}}_3 \mathrm{and} {\mathrm{AlCl}}_3$ are both Lewis acids and ${\mathrm{BCl}}_3$ is stronger than ${\mathrm{AlCl}}_3$

• B

  ${\mathrm{BCl}}_3 \mathrm{and} {\mathrm{AlCl}}_3$ both are Lewis acids and ${\mathrm{AlCl}}_3$ is stronger than ${\mathrm{BCl}}_3$

• C

  ${\mathrm{BCl}}_3 \mathrm{and} {\mathrm{AlCl}}_3$ are both equally strong Lewis acids

• D

  Both ${\mathrm{BCl}}_3 \mathrm{and} {\mathrm{AlCl}}_3$ are not Lewis acids.