What is the phylum of the frog?

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 $Cephalochordata$.

In both chordates and non-chordates,the intestine develops from which germ layer?

$A:$ Amphioxus is not a vertebrate.
$R:$ Amphioxus is not a chordate.

One of the primary characteristics of chordates is:

Echinoderms and chordates have