Ans.
The given diagram represents a cladogram, which is used to show evolutionary relationships between various organisms or species.
The intersection points between the lines show the common ancestors, which evolved into different organisms at the end of the branches, as A, B, C, D.
The first branch end (A) represents that most primitive organism, while the last branch end (D) represents the most recent organism.
Thus, the correct answer is option). 'organism A is the most primitive organism.'