Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Members of subphylum vertebrates possess notochord during the embryonic period. The notochord is replaced by a cartilaginous or bony vertebral column in the adult.
Reason R: Thus all chordates are vertebrates not all vertebrates are chordates.
In the light of the above statements choose the correct answer from the option given below