Which acid is not an arrhenius acid

$N{a_2}{B_4}{O_7}.10{H_2}O \xrightarrow{\Delta } X + NaB{O_2} + {H_2}O$

$X + C{r_2}{O_3}\xrightarrow{\Delta }Y$ (Green coloured)

$X$ and $Y$ are

The tendency of $BF_3, BCl_3$ and $BBr_3$ to behave as Lewis acid decreases in the sequence

$B{X_3} + N{H_3}\xrightarrow{{R.T}}B{X_3}.N{H_3} + Heat\,of\,adduct\,formation\,\left( {\Delta H} \right)$ The numerical value of $\Delta H$ is found to be maximum for

$BCl_3$, exists as monomer whereas $AlCl_3$ is dimerized through halogen bridging. Give reason. Explain the structure of the dimer of $AlCl_3$ also. 

The electrochemical extraction of aluminum from bauxite ore involves.

$(A)$ the reaction of $Al _2 O _3$ with coke ($C$) at a temperature $>2500^{\circ} C$.

$(B)$ the neutralization of aluminate solution by passing $CO _2$ gas to precipitate hydrated alumina $\left( Al _2 O _3 .3 H _2 O \right)$

$(C)$ the dissolution of $Al _2 O _3$ in hot aqueous $NaOH$.

$(D)$ the electrolysis of $Al _2 O _3$ mixed with $Na _3 AlF _6$ to give $Al$ and $CO _2$.