Which of the following is the strongest reducing agent?

Observe the following statements:
Statement-$I$: Both $LiF$ and $CsI$ have low solubility in water.
Statement-$II$: Low solubility of $LiF$ in water is due to its high lattice enthalpy,and that of $CsI$ is due to its smaller hydration enthalpy of ions.

Which element from the following is used in photoelectric cells?

$A$ chemical $A$ is used for the preparation of washing soda to recover ammonia. When $CO_2$ is bubbled through an aqueous solution of $A$,the solution turns milky. It is used in white washing due to its disinfectant nature. What is the chemical formula of $A$?

Which of the following alkali metals has a density greater than water?

Give two uses of $KOH$.