Which of the following statements is correct?

• A
  $BCl_3$ and $AlCl_3$ are both Lewis acids,and $BCl_3$ is stronger than $AlCl_3$.
• B
  $BCl_3$ and $AlCl_3$ are both Lewis acids,and $AlCl_3$ is stronger than $BCl_3$.
• C
  $BCl_3$ and $AlCl_3$ are both equally strong Lewis acids.
• D
  $BCl_3$ and $AlCl_3$ are not Lewis acids.