Which of the following are mixed anhydrides?

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 of the following is used in the preparation of chlorine?

Which of the following is the correct order of reactivity of halogens with alkali?

Which one of the following is formed apart from sodium chloride when chlorine reacts with hot concentrated sodium hydroxide?

The halogen acid used in the preparation of aqua regia is