Read the following statements carefully: A. All chordates possess a dorsal solid nerve cord. B. In vertebrates, the notochord is replaced by a cartilaginous or bony vertebral column in the embryonic stage. C. Protochordates are exclusively marine animals. D. In Cephalochordata, the notochord extends from head to tail region and is persistent throughout their life. How many of the above statements are correct?

Step-by-step solution

Statement A is incorrect because chordates are characterised by the presence of a dorsal hollow nerve cord, not a solid one. Non-chordates typically possess a solid nerve cord. Statement B is incorrect because in vertebrates, the notochord is present during the embryonic period and is replaced by a cartilaginous or bony vertebral column in the adult stage, not the embryonic stage. Statement C is correct as the subphyla Urochordata and Cephalochordata are often referred to as protochordates and are exclusively marin