Final answer:
The pair Euryarchaeota and Crenarchaeota from the domain Archaea share the most recent common ancestor according to the phylogenetic tree.
Step-by-step explanation:
When analyzing a phylogenetic tree, it is important to look at the branching points, or nodes, that represent common ancestors of the subsequent branches. In this case, we are comparing different subgroups within the prokaryotic domains, Bacteria and Archaea. Eukaryotes, which include humans and other animals, are said to share a more recent common ancestor with Archaea than with Bacteria. Among the groups listed, Euryarchaeota and Crenarchaeota both belong to the domain Archaea, making them more closely related to each other than to any of the Bacteria groups mentioned. Their common ancestor would be the one indicative of the origin of Archaea. Consequently, the pair Euryarchaeota ... Crenarchaeota share the most recent common ancestor.