Based on the cladogram, which of these organisms are the most closely related?

For a cladogram the closer the organisms are, the closer they are related.

Explanation:

Each branching off represents a change in the species, so the closer they are, the more traits they will share

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).