Which of the following is described as a protochordate?

Which of the following is incorrect for $Urochordata$?

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 $Cephalochordata$.

All chordates possess $..........$.

Definition / Explanation: Notochord

The most important distinctive character of $Chordata$ is the presence of