Which of the following pathways is part of the cloaca in vertebrates?

Which of the following cannot be considered a characteristic of non-chordates?

Which of the following distinguishes chordates from non-chordates?

Name the following:
$A$ chordate animal having flame cells as excretory structures.

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:

The notochord is .........