The Carcass of a Newly Discovered Deep-Diving Species of Whale

The carcass of a newly discovered deep-diving species of whale washes up on shore, and biologists scramble to study the adaptations that allow this species to circulate blood when it is under pressure at depth.A cross section of its flipper shows what seem to be a vein and an artery running parallel.The artery would be the structure

A) with the largest interior diameter.
B) with more muscle tissue and elastin in the wall.
C) lined with endothelium.
D) with valves to prevent backflow.
E) with an outer connective tissue layer.