Which of the following possesses an endoskeleton made of cartilage or bone?

Which one of the following features are true for chordates?
$(a)$ Heart is ventral.
$(b)$ Pharyngeal gill slits present.
$(c)$ Central nervous system is ventral,solid and single.
$(d)$ Post-anal tail is present.
$(e)$ Notochord is present.
Choose the most appropriate answer from the options given below:

Which of the following animals is known as an invertebrate chordate?

The notochord is restricted to the tail region only in:

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

Which of the following is $NOT$ found in vertebrates?