Boron halides are Lewis acids because.....

Which of the following produce an alkaline solution when dissolved in water?
$(i)$ Borax
$(ii)$ Potash alum
$(iii)$ $SO_2$
$(iv)$ $SO_2(OH)_2$

Which of the following boron compounds is the hardest?

The geometry around boron in the product '$B$' formed from the following reaction is
$BF_{3} + NaH \xrightarrow{450 \ K} A + NaF$
$A + NMe_{3} \rightarrow B$

Match the following compounds in List-$I$ with their properties/names in List-$II$.

List-$I$ (Compound)	List-$II$ (Property/Name/Structure)
$A$. $H_3BO_3$	$1$. Dimeric form
$B$. $AlCl_3$	$2$. Back bonding
$C$. $B_3N_3H_6$	$3$. Hydrogen bonding
$D$. $BF_3$	$4$. Inorganic benzene

What happens when:
$(a)$ Borax is heated strongly,
$(b)$ Boric acid is added to water,
$(c)$ Aluminium is treated with dilute $NaOH$,
$(d)$ $BF_{3}$ is reacted with ammonia?