Which of the following is a true alum?

The total number of acidic oxides from the following list is: $NO$,$N_2O$,$B_2O_3$,$N_2O_5$,$CO$,$SO_3$,$P_4O_{10}$

$X$ reacts with aqueous $NaOH$ to form $Y$ and releases $H_2$ gas. When the aqueous solution of $Y$ is heated at $323 \ K - 333 \ K$ and $CO_2$ gas is passed through it,it yields $Al_2O_3 \cdot xH_2O$ (often represented as $Al(OH)_3$) and $Z$. Heating $Z$ at $1200 \ ^\circ C$ gives $Al_2O_3$. Identify $X, Y,$ and $Z$.

Kernite and cryolite are the minerals of two elements $X$ and $Z$. Respectively $X$ and $Z$ are

$B(OH)_3 + NaOH \rightleftharpoons NaBO_2 + Na[B(OH)_4] + H_2O$
How can this reaction be made to proceed in the forward direction?

$AlCl_3$ in water at $pH < 7$ forms