How many of the following are Lewis acids?

${\mathrm{CCl}}_4,\mathrm{Si}{F}_4,{\mathrm{PH}}_3,{\mathrm{BCl}}_3,{\mathrm{AlCl}}_3,{\mathrm{CH}}_4$

${\mathrm{BCl}}_3,{\mathrm{AlCl}}_3\text{ and }\mathrm{Si}{F}_4\text{ are Lewis acids.In }{\mathrm{BCl}}_3,{\mathrm{AlCl}}_3$ central atoms B,Al have vacant p-orbitals and Incomplete octet thus they behave as Lewis acids. ${\mathrm{SiCl}}_4$ can accept lone pair of electron in d-orbitals of silicon.  Hence it can acts as Lewis acid.