In which of the following,a salt of the type $KMO_2$ is obtained?

Which of the following statements is incorrect?

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:

What is $Z$ in the following reactions?
$BCl_3 + H_2 \xrightarrow[450^{\circ}C]{Cu-Al} X + HCl$
$X \xrightarrow{\text{methylation}} Z$

Aluminium reacts with $NaOH$ and forms compound '$X$'. If the coordination number of aluminium in '$X$' is $6$, the correct formula of $X$ is:

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.