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

Provide definitions/explanations for the following terms:
$(i)$ Cephalochordata
$(ii)$ Pseudocoelomates

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 $Cephalochordata$.

Select the correct option for the $notochord$:

In which of the following is a closed circulatory system found?

Which of the following is a group of invertebrate chordates?