Amongst halogens,fluorine is the most powerful oxidizing agent because:

$Cl_2$ gas is dried over which of the following?

Chlorine gas is dried over

The colour of the $X_2$ molecules of group $17$ elements changes gradually from yellow to violet down the group. This is due to
[$A$] the physical state of $X_2$ at room temperature changes from gas to solid down the group
[$B$] decrease in $HOMO-LUMO$ gap down the group
[$C$] decrease in $\pi^*-\sigma^*$ gap down the group
[$D$] decrease in ionization energy down the group

The reaction of concentrated $HNO_3$ with iodine produces ....

Which one is the anhydride of $HClO_4$?