Answer;
-Descendants of organism (d) have legs.
-Birds and ray-finned fishes have a notochord and jaws.
-Rays and frogs have a vertebral column.
-Organism (a) is a common ancestor of all chordates.
-Mammals and turtles are more closely related than are lungfishes and sharks.
Explanation;
Phylogenetic trees is a diagram that represents evolutionary relationships among organisms.
The branching pattern reflects how species or other groups evolved from a series of common ancestors.