Which of the following is called "Lunar Caustic"?

The bleaching action of bleaching powder is due to the formation of

The correct statement$(s)$ about the oxoacids,$HClO_4$ and $HClO$,is(are):
$[A]$ $HClO_4$ is more acidic than $HClO$ because of the resonance stabilization of its anion.
$[B]$ $HClO_4$ is formed in the reaction between $Cl_2$ and $H_2O$.
$[C]$ The central atom in both $HClO_4$ and $HClO$ is $sp^3$ hybridized.
$[D]$ The conjugate base of $HClO_4$ is a weaker base than $H_2O$.

Which halogen is known to cause the reaction given below:
$2 Cu^{2+} + 4 X^{-} \rightarrow Cu_2 X_{2(s)} + X_2$

Discuss the anomalous behaviour of fluorine.

In the following reaction,identify the nature of the product formed by the complete hydrolysis of the underlined atom at $R.T.$:
$\underline{I}_2O_5 + H_2O \longrightarrow HIO_3$