Which of the following animals possesses a post-anal tail?

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

Assertion $(A)$: $Ascidia$ and $Salpa$ are placed under sub-phylum $Urochordata$.
Reason $(R)$: In $Ascidia$ and $Salpa$,notochord is present only in larval tail.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following animals is not a vertebrate?

Formation of notochord or the central axial chord in vertebrates is known as

The notochord is an organ derived from which embryonic layer?