Which one of the following is the correct statement?

The correct statements from the following are:
$(A)$ The decreasing order of atomic radii of group $13$ elements is $Tl > In > Ga > Al > B$.
$(B)$ Down the group $13$ electronegativity decreases from top to bottom.
$(C)$ $Al$ dissolves in dil. $HCl$ and liberates $H_2$,but conc. $HNO_3$ renders $Al$ passive by forming a protective oxide layer on the surface.
$(D)$ All elements of group $13$ exhibit a highly stable $+1$ oxidation state.
$(E)$ Hybridisation of $Al$ in $[Al(H_2O)_6]^{3+}$ ion is $sp^3d^2$.
Choose the correct answer from the options given below:

Which of the following does not exist in free form?

Which of the following statements is correct?

In the reaction $B_2H_6 + 2KOH + 2X \to 2Y + 6H_2$,$X$ and $Y$ are respectively

Borax has the molecular formula