Answer:
The correct answer will be- sister group or crown group.
Explanation:
A clade is the group of the organism which has descended from a common ancestor. The visual representation of clade is known as a cladogram which shows the relationship between organism in tree-form.
In the visual representation, when two branches appear growing from a common branch, the two branches will be called "sister groups or crown groups".
Since three mammalian namely monotreme, marsupials, and Eutheria are thought to have descended from a common ancestor of mammals, therefore, they will be called "sister groups".
Thus, the sister group or crown group is the correct answer.
