Which of the following is another characteristic of animals possessing a solid nerve cord?

What is the location and function of pharyngeal gill slits?

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 $Cephalochordata$.

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

Statement-$1$ : Cephalochordata bears notochord all along the body throughout life.
Statement-$2$ : Urochordate bears vertebral column only in tail region throughout the life.
Then which is correct?

One of the primary characters of chordates is