Answer the following question given this paragraph: 

distinctly differ from the adult form, spending 3 to 15 years as suspension feeders. Once they attain sexual maturity, the adults reproduce and die within days. Lampreys possess a notochord as adults; however, this notochord is surrounded by a cartilaginous structure called an arcualia, which may resemble an evolutionarily early form of the vertebral column.


Q: What do we call the cartilaginous structure that surrounds the notochrod?

 Choices:

- osteocytes

- clavicle

- membrane

- arcualia

A:
arcualia
