Which of the following can be used to extinguish a fire caused by alkali metals?

$Na + Al_2O_3$ $\xrightarrow{\text{High temperature}} X$ $\xrightarrow[\text{water}]{CO_2} Y$; compound $Y$ is

Which of the following has the highest solubility product?

Which gas is released when $Na_2CO_3$ is heated?

Which of the following is the chemical formula for dolomite?

Among the following,the number of metals that can be used as electrodes in a photoelectric cell is $.......$ (Integer answer)
$A. Li$
$B. Na$
$C. Rb$
$D. Cs$