Echinoderms and chordates have

Which one of the following is a chordate but not a vertebrate?

Vertebrates possess which of the following characteristics?

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:

In which of the following is the notochord absent?

Which of the following statements is $NOT$ correct for Chordates?