Which of the following statements is $NOT$ correct for Chordates?

Echinoderms and chordates have

Which of the following organisms possess an endoskeleton?

Development of the mouth later than the anus during embryonic development is a condition called:

Besides $Annelida$ and $Arthropoda$,metamerism is found in

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.