Which of the following are Lewis acids?

Here, BCl3, AlCl3, SiCl4 are Lewis acids because in all these compounds the central atom is electron deficient. In BCl3, B contains only 6 electrons and in AlCl3, Al also contains only 6 electrons. In SiCl4, Si is also electron deficient since it has vacant d-orbitals, thus acting as a Lewis acid.