Which of the following is not a subphylum of Chordata?

The body is divided into head and trunk in:

Give a scientific reason: Annelids are considered evolutionary precursors of molluscs.

Excretion by protonephridia with solenocytes is a characteristic of

Which of the following statements are true for the phylum $Chordata$?
$(a)$ In $Urochordata$,the notochord extends from head to tail and is present throughout their life.
$(b)$ In $Vertebrata$,the notochord is present during the embryonic period only.
$(c)$ The central nervous system is dorsal and hollow.
$(d)$ $Chordata$ is divided into $3$ subphyla: $Hemichordata$,$Tunicata$,and $Cephalochordata$.

Which set of terms would most likely be used in a description of the nervous system of chordates?