Julia is trying to place a duckbilled platypus, lizard, bear, and monkey on a phylogenetic tree. she learns that the duckbilled playpus, bear, and monkey are classified as mammals. she also learns that mammals share a common ancestor with reptiles. what additional piece of information will be most to julia to properly build her phylogenetic tree?

To properly build the phylogenetic tree, Julia needs information that can connect any of mentioned mammals (bear and monkey) to reptiles. And that could be only the fact that a duckbilled platypus lays eggs similarly like reptiles. So, the platypus is a mammal and relationship with bear and monkey in that way exist, but laying eggs is not characteristic for other mammals.