Which of the following halogens does not form oxoacids?

Given below are two statements: Statement $(I)$: Oxidising power of halogens decreases in the order $F_2 > Cl_2 > Br_2 > I_2$,which is the basis of "Layer test". Statement $(II)$: "Layer test" to identify $Br_2$ and $I_2$ in aqueous solution involves the oxidation of bromide or iodide into $Br_2$ or $I_2$ respectively with $Cl_2$,which is a type of displacement redox reaction. In the light of the above statements,choose the correct answer from the options given below:

Which of the following are mixed anhydrides?

In $KI$ solution,$I_2$ readily dissolves and forms:

Who established the elemental nature of chlorine?

Mark the strongest acid.