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

What is the correct classification of Ascidia?

In which of the following is a closed circulatory system found?

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:

There has been an increase in the number of chambers in the heart during the evolution of vertebrates. Name the classes of vertebrates that have two,three,and four-chambered hearts.

Which of the following phyla possess a post-anal tail at some stage of their life?