The geometry around boron in the product '$B$' formed from the following reaction is
$BF_{3} + NaH \xrightarrow{450 \ K} A + NaF$
$A + NMe_{3} \rightarrow B$

Which of the following oxides is acidic in nature?

Select the incorrect statement:
$a$. $PCl_5$ forms a weak monobasic acid during hydrolysis.
$b$. In $B_3N_3H_6$,nucleophilic attack occurs on the $B$ atom.
$c$. $Al_2Cl_6$ is a polar and planar molecule.
$d$. In $AlF_3$,the hybridization of $Al$ is $sp^2$.

Which of the following statements is not true about borax?

The Lewis acid character of boron trihalides follows the order:

What are the correct statements about the elements of group $13$ given below?
$(I)$ The stability of $+1$ oxidation state follows the order $Tl > In > Ga$
$(II)$ Boron has the lowest melting point and boiling point as it is a non-metal
$(III)$ Boron shows a maximum covalency of $4$ in its compounds
$(IV)$ The order of atomic radius is $Ga > Al > In$
$(V)$ Aluminium is passive to concentrated nitric acid