In which of the following molecules is a hydrogen bridge bond present?

What is the molecular formula of borazole?

$H_3BO_3$ is

Borax is actually made of two tetrahedra and two triangular units joined together and should be written as: $Na_2[B_4O_5(OH)_4] \cdot 8H_2O$. Consider the following statements about borax:
$a.$ Each boron atom has four $B-O$ bonds
$b.$ Each boron atom has three $B-O$ bonds
$c.$ Two boron atoms have four $B-O$ bonds while other two have three $B-O$ bonds
$d.$ Each boron atom has one $-OH$ group
Select correct statement$(s)$:

Group-$13$ elements react with $O_2$ to form oxides of the type $M_2O_3$ ($M =$ element). Which among the following is the most basic oxide?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$ : The stability order of $+1$ oxidation state of $Ga$,$In$ and $Tl$ is $Ga < In < Tl$.
Reason $R$ : The inert pair effect stabilizes the lower oxidation state down the group.
In the light of the above statements,choose the correct answer from the options given below :