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The arrangement of metals in decreasing order of their reactivity is called reactivity series of metals.
The order of reactivity of metals is as follows,
Potassium > Sodium > Magnesium > Aluminium > Zinc > Iron > Copper > Silver > Gold.
Therefore, according to this order, we can arrange the order of reactivity of metals given in the question as:
Potassium> Aluminium> Copper