The Lewis acid strength of following molecule is in the order:

Arrangement of back bonding ${\mathrm{BF}}_3<{\mathrm{BCl}}_3<{\mathrm{BBr}}_3$

Back bonding  $2p-2p, 2p-3p, 2p-4p$

Back bonding strength increases with ability to behave as a Lewis acid decreasing.

${\mathrm{BF}}_3<{\mathrm{BCl}}_3<{\mathrm{BBr}}_3$

Due to the dominance of inductive action over back bonding in silicone halides, Lewis acid character is determined by inductive effect. Hence the Lewis acid character's order:

${\mathrm{SiF}}_4>{\mathrm{SiCl}}_4>{\mathrm{SiBr}}_4$

Hence, options C and D are correct.