Final answer:
Taxonomists use a phylogenetic tree, specifically a cladogram, to understand the phylogenetic relationship between species.
Step-by-step explanation:
Taxonomists use a phylogenetic tree to understand the phylogenetic relationship between species. A phylogenetic tree is a diagram that shows the evolutionary pathways and relationships between organisms. It helps in tracing common ancestry between two species by visually representing their evolutionary history.
Option A) Cladogram is the correct answer. A cladogram is a type of phylogenetic tree that is used to represent the relationship between organisms based on shared characteristics.