Maximum number of atoms which are present in one plane of $H_3BO_3$?

The number of $P-H$ bond$(s)$ in $H_3PO_2, H_3PO_3$ and $H_3PO_4$,respectively,is

Which of the following statements about $BF_4^{-}$ and $AlF_6^{3-}$ are correct?
$(i)$ $B$ and $Al$ differ in their oxidation states.
$(ii)$ $B$ and $Al$ differ in their covalency.
$(iii)$ $B$ obeys the octet rule.
$(iv)$ $B$ and $Al$ are in diagonal relationship.

Marine plants are an important source of which of the following?

Complete the following chemical equations:
$4BF_{3} + 3LiAlH_{4} \to 2B_{2}H_{6} (X) + 3LiF + 3AlF_{3}$
$B_{2}H_{6} (X) + 6H_{2}O \to 2H_{3}BO_{3} (Y) + 6H_{2}$
$B_{2}H_{6} (X) + 3O_{2} \xrightarrow{\Delta} B_{2}O_{3} + 3H_{2}O$

Group-$13$ elements react with $O_2$ to form oxides of the type $M_2O_3$ ($M =$ element). Which among the following is the most basic oxide?