To which group does $Salpa$ belong?

In vertebrates,the notochord is replaced by which structure during the embryonic stage?

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 $(R)$: Notochord is replaced by vertebral column in the adult vertebrates.
In the light of the above statements,choose the most appropriate answer from the options given below:

What are animals called if they possess a notochord?

$A$ rod-like structure formed on the dorsal side during embryonic development in some animals, which is mesodermally derived:

Echinoderms and chordates have