The geometry around boron in the product 'B' formed from the following reaction is

$$ \begin{aligned} &\mathrm{BF}_{3}+\mathrm{NaH} \stackrel{450 \mathrm{~K}}{\rightarrow} \mathrm{A}+\mathrm{NaF} \\\\ &\mathrm{A}+\mathrm{NMe}_{3} \rightarrow \mathrm{B} \end{aligned} $$

The interhalogen compound formed from the reaction of bromine with excess of fluorine is a :

A $$\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{}^{573\,K}} $$ Red phosphorus $$\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{under\,pressure}^{heat\,;\,803\,K}} $$ B

Red phosphorus is obtained by heating "A" at 573 K, and can be converted to "B" by heating at 803 K under pressure.

A and B, respectively, are

Aqueous solution of which of the following boron compounds will be strongly basic in nature?