Answer : The correct answer is -
A. backbone.
Notochord can be described as a rodlike, flexible structure, composed of mesoderm derived cells. It is considered as the fundamental structural element in chordates and of the early embryo of vertebrates as it plays a organizational role in the development of nervous.
In later development of vertebrates, notochord becomes a part of the vertebral column.
In other words, it gets replaced during embryonic development of embryo by backbone in higher chordates or vertebrae of the vertebral column.
Thus, backbone is the right answer.
