Species X and Species Z belong to the same domain.
Step-by-step explanation:
Depending on the rRNA sequences , the five kingdoms of the living world were grouped into three domains named as Bacteria, Archaea and Eukarya.
Domains were then further classified into Kingdoms.
Based on the above information we can conclude that domain is a rank above Kingdom.
In the given question, X and Y belong to the same domain and Y and Z belong to the same kingdom.
So it is clear that Z belongs to the domain to which Y belongs.
Thus, X and Z belongs to the same domain because Y belongs to the domain to which X belongs.