Which of the following oxides is amphoteric in nature?

$A$ 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.

Which one is a pseudo alum?

Chemically,borax is:

Which of the following statements is not correct about diborane $(B_2H_6)$?

Which of the following on hydrolysis produces diborane $(B_2H_6)$?