Step-by-step explanation:
1. It is a redox reaction because it is stable
2. 2Al(s) ->2Al(NO3)3(aq) (oxidation)
3Cu(NO3)2(aq) ->3Cu(s) (reduction)
3. 2Al(s) is being oxidised to 2Al(NO3)3(aq)
3Cu(NO3)2(aq) is being reduced to 3Cu(s)
4. 3Cu(NO3)2(aq) is the oxidising agent
2Al(s) is the reducing agent