The acid which forms two series of salts is

Hydrated $AlCl_3$ is used as :

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{B}F_3 + 3H_2O \longrightarrow H_3BO_3 + 3HF$

What does orthoboric acid contain?

The alum used for purifying water is

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: