Refer to the periodic table and answer the following questions:
$(a)$ Select the possible non-metals that can show disproportionation reaction.
$(b)$ Select three metals that can show disproportionation reaction.

(N/A) In disproportionation reactions,one of the reacting substances always contains an element that can exist in at least three oxidation states.
$(a)$ $P, Cl$,and $S$ can show disproportionation reactions as these elements can exist in three or more oxidation states.
$(b)$ $Mn, Cu$,and $Ga$ can show disproportionation reactions as these elements can exist in three or more oxidation states.