The Lewis acid character of boron trihalides follows the order:

The reason for boric acid being polymeric is .....

Anhydrous $AlCl_3$ cannot be obtained from which of the following reactions?

Boron cannot form which one of the following anions?

The correct statements from the following are:
$(A)$ Ionic radii of trivalent cations of group $13$ elements decrease down the group.
$(B)$ Electronegativity of group $13$ elements decreases down the group.
$(C)$ Among the group $13$ elements, Boron has the highest first ionisation enthalpy.
$(D)$ The trichlorides and triiodides of group $13$ elements are covalent in nature.
Choose the correct answer from the options given below:

Boron compounds act as Lewis acids due to .....