Which of the following pairs will give displacement reactions?

The correct option is AgNO3solution and copper metal. Metals higher in the activity series are more reactive and can displace less reactive metals.
(a) NaClsolution and copper metal: Na is more reactive than Cu, thus it will not give a displacement reaction.
(b) MgCl2solution and aluminium metal: Al cannot replace Mg because it is lower on the reactivity series.
(c) FeSO4solution and silver metal: Ag cannot replace Fe because it is lower on the reactivity series.
(d) AgNO3solution and copper metal: Ag can be replaced by Cu as it is above silver in the reactivity series. Therefore, this pair will give a displacement reaction.
AgNO3 + Cu → Cu(NO3)2 + Ag
Hence, option D is correct.