Answer:
2.Ag+
Step-by-step explanation:
This problem tests our knowledge/understanding of the electro-chemical series.
Electrochemical series or activity series is a list that describes the arrangement of elements in order of their increasing electrode potential values.
In the electro-chemical series metals placed above can displace metals below from their salt solutions.
In this question given the series as stated
1. Fe2+
2.Ag+
3.Zn2+
4.Al3+
In the series we have metals stated as Zn>Fe>Cu>Ag.
Cu will displace silver Ag+ because it is below it in the series