By which developmental similarity are Echinoderms related to Chordates?

The notochord is derived from which germ layer?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ All vertebrates are chordates but all chordates are not vertebrates.
Reason $(R):$ The members of subphylum Vertebrata possess a notochord during the embryonic period; the notochord is replaced by a cartilaginous or bony vertebral column in adults.
In the light of the above statements,choose the correct answer from the options given below:

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

Assertion: Notochord is a mesodermally derived rod-like structure formed on the dorsal side during embryonic development of chordates.
Reason: Notochord is replaced by the vertebral column in the adult vertebrate.

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: