Boron halides are:
A.Electron deficient compounds
B.Ionic compounds
C.Lewis bases
D.Used as refractory compounds

Hint: A halide is a binary phase, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen. Halogens are basically anion forms of halogen atoms and are found in the Group $17$of the periodic table. They exists in natural water sources like rivers, lakes and streams due to their high solubility in water and the common halides that are found are fluorine, chloride and bromine.

Complete answer:
Boron halides, such as $B{F_3}$ or $BC{l_3}$are electron deficient molecules as they do not have an octet of electrons surrounding the boron atom. As a result, they tend to act as strong Lewis acids by accepting electrons from many Lewis bases to form stable acid-base adducts and hence they also act as catalysts for several important organic reactions.
Therefore, we can say that boron halides are electron deficient compounds which satisfies option (A).

Note:
Boron halides are planar and has a bond angle of ${120^ \circ }$ and follows $s{p^2}$ hybridization. However, $B - X$ bond lengths that are found experimentally are shorter than the values calculated using covalent single bond radii of boron and the halogens.
Boron halides undergo many reactions in addition to Lewis acid-base reaction and the most typical compounds containing covalent bonds between a non-metal and a halogen. These compounds react vigorously with water as a result of hydrolysis reactions and yield boric acid and hydrogen halide. This can be represented by the following general reaction.
$B{X_3} + 3{H_2}O \to {H_3}B{O_3} + 3HX$