Which of the following is an amphoteric hydroxide?

Hydrolysis of $BCl_3$ gives $X$,which on treatment with sodium carbonate produces $Y$. $X$ and $Y$,respectively,are

Which of the following hydroxides is acidic?

The formula of borax is

Select the correct statement about the hydrolysis of $BCl_3$ and $NCl_3$.

$A$ compound $(A)$ of boron reacts with $NMe_3$ to give an adduct $(B)$ which on hydrolysis gives a compound $(C)$ and hydrogen gas. Compound $(C)$ is an acid. Identify the compounds $A, B$ and $C$. Give the reactions involved.