Identify the correct statements from the following:
$a$) Borax gives blue coloured $Co(BO_2)_2$ when heated with $Co^{2+}$ salt.
$b$) The correct formula of Borax is $Na_2[B_4O_5(OH)_4] \cdot 8H_2O$.
$c$) Trihalides of boron are Lewis bases.

Match the List-$I$ with List-$II$.

List-$I$ (Element)	List-$II$ (Application)
$A$. $Cs$	$I$. High temperature thermometer
$B$. $Ga$	$II$. Water repellent sprays
$C$. $B$	$III$. Photoelectric cells
$D$. $Si$	$IV$. Bullet proof vest

Choose the most appropriate answer from the options given below:

The correct statement$(s)$ for orthoboric acid $(H_3BO_3)$ is/are:
$(A)$ It behaves as a weak acid in water due to self-ionization.
$(B)$ Acidity of its aqueous solution increases upon addition of ethylene glycol.
$(C)$ It has a three-dimensional structure due to hydrogen bonding.
$(D)$ It is a weak electrolyte in water.

The bonding in diborane $(B_2H_6)$ can be described by

What is the molecular formula of borazole?

Which of the following statements is correct for boric acid?