In the reaction $B(OH)_{3} + 2 H_{2}O \rightarrow [B(OH)_{4}]^{-} + H_{3}O^{+}$,$B(OH)_{3}$ functions as:

What is $Z$ in the following reactions?

Which gases are released when aluminum reacts with concentrated $HCl$ and concentrated $NaOH$,respectively?

Which element belongs to the family of elements that also includes the element gallium?

In the reactions $I$ and $II$,the covalencies of $Be$ and $Al$ in $X$ and $Y$ are respectively:
$I$ $Be(OH)_2 + NaOH \text{ (excess)} \rightarrow X$
$II$ $Al(OH)_3 + NaOH \text{ (excess)} \rightarrow Y$

The correct order of Lewis acidity for $BX_3$ is: