Which of the following groups of characters is present in all chordates at some stage in their life?

What is the classification of the subphylum $Vertebrata$?

Apart from Annelida and Arthropoda,metamerism is also exhibited by ............ .

What is the location and function of the nerve cord in chordates?

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:

Which of the following is a chordate feature,not shared by the non-chordates?