Which among the following statement(s) is(are) true for the extraction of aluminium from bauxite?

$(A)$ Hydrated $Al _2 O _3$ precipitates, when $CO _2$ is bubbled through a solution of sodium aluminate.

$(B)$ Addition of $Na _3 AlF _6$ lowers the melting point of alumina.

$(C)$ $CO _2$ is evolved at the anode during electrolysis.

$(D)$ The cathode is a steel vessel with a lining of carbon.

When borax is heated with $CoO$ on a platinum loop, blue coloured bead formed is largely due to

When $BCl_3$, is treated with water, it hydrolyses and forms $[B(OH)_4]^-$ only whereas $AlCl_3$ in acidified aqueous solution forms $[Al(H_2O)_6]^{3+}$ ion. Explain what is the hybridizations of boron and aluminum in these species?

Write balanced equations for : 

$(i)\,B{F_3} + LiH \to $

$(ii)\,{B_2}{H_6} + {H_2}O \to $

$(iii)\,NaH + {B_2}{H_6} \to $

$(iv)\,{H_3}B{O_3}\xrightarrow{\Delta }$

$(v)\,Al + NaOH \to $

$(vi)\,{B_2}{H_6} + N{H_3} \to $

$(BN)_n$  exists in