What is the correct order of melting points for the elements of Group $13$?

Pick the correct statement.
$I$. Borax is a white crystalline solid containing $\left[B_4 O_5(OH)_4\right]^{2-}$ units.
$II$. The aqueous solution of borax is acidic in nature.
$III$. Cobalt gives a blue color in the borax bead test.

Give the physical and chemical properties of orthoboric acid $(H_3BO_3)$.

Which of the following substances is the strongest acid?

Given below are the statements about diborane.
$(a)$ Diborane is prepared by the oxidation of $NaBH_{4}$ with $I_{2}$.
$(b)$ Each boron atom is in $sp^{2}$ hybridized state.
$(c)$ Diborane has one bridged $3$ centre$-2-$electron bond.
$(d)$ Diborane is a planar molecule.
The option with correct statement$(s)$ is :

The alum used for purifying water is