In chordates,the alimentary canal is located in which position relative to the nerve cord?

In chordates,the brain is formed from which of the following structures?

In which of the following is the $rotatory$ $organ$ (wheel organ) found?

All vertebrates possess ......... .

Which of the following possesses a non-ganglionated nerve cord?

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.