Fluorosis disease is caused due to the reaction of ...... with excess of fluoride in the body.

$A$ compound $(M_2O_2)$ of group $I$ element $(M)$ hydrolyses to form $M^{+}$,$OH^{-}$ and $X$. Another compound $(M'O_2)$ of group $I$ element $(M')$ hydrolyses to form $(M')^{+}$,$OH^{-}$,$X$ and $Y$. What are $X$ and $Y$ respectively?

In the case of alkali metals,the covalent character decreases in the order

Which of the following is $NOT$ present in baking powder?

Which of the following is not correctly matched?

Number of amphoteric compounds among the following is ...........
$A$. $BeO$
$B$. $BaO$
$C$. $Be(OH)_2$
$D$. $Sr(OH)_2$