Adult Tunicates (Urochordates) Lack Notochords, However, Larval Urochordates Have Them

Adult tunicates (urochordates) lack notochords, however, larval urochordates have them and use them to ________.

A) aid in swimming; adults are sessile and thus no longer propel themselves.
B) stiffen their bodies; in adults, the notochord is replaced by a column of bone.
C) induce tissue differentiation; in adults, tissue is already differentiated.
D) organize their nervous systems; adults' nervous systems are fully developed and do not change.