Read the following statements regarding the phylum Chordata: (A) In Urochordata, the notochord is present only in the larval tail. (B) In Cephalochordata, the notochord extends from the head to the tail region and is persistent throughout life. (C) Members of the subphylum Vertebrata possess a notochord during the embryonic period. (D) In all chordates, the notochord is replaced by a cartilaginous or bony vertebral c

Step-by-step solution

Statements (A), (B), and (C) are correct descriptions of the subphyla Urochordata, Cephalochordata, and Vertebrata respectively, as per NCERT. Statement (D) is incorrect because the replacement of the notochord by a cartilaginous or bony vertebral column occurs only in the subphylum Vertebrata, not in all chordates. Protochordates (Urochordata and Cephalochordata) lack a vertebral column. Thus, exactly three statements are correct. Answer: Three