Final answer:
Cooksonia, a primitive early vascular plant, is associated with the more primitive sporangium type known as A. Eusporangium.
Step-by-step explanation:
The association with Cooksonia refers to the type of sporangium it possessed.
Cooksonia is an extinct genus of very early vascular plants and is known for its branching structure with sporangia at the tips of each branch.
Given the two options, Eusporangium and Leptosporangium, Cooksonia is typically associated with Eusporangium.
Because it is one of the earliest land plants, and the eusporangium structure is considered more primitive compared to the derived leptosporangiate condition found in later-evolving vascular plants, such as modern ferns.
Thus, the answer to the question, "Which of the following is associated with Cooksonia?" would be A. Eusporangium.