Mode of feeding in tunicates is

The body of a urochordate is enclosed in a

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:

Post-anal tail is present in

Give a scientific reason: Annelids are considered evolutionary precursors of molluscs.

Give three major differences between chordates and non-chordates and draw a schematic sketch of a chordate showing those features.