Question

The structure present in all adult vertebrates is:

• A. Notochord
• B. Dorsal tubular nerve cord
• C. Pharyngeal gill slits
• D. All of these

Answer 1

The correct option is B Dorsal tubular nerve cord

• The notochord in the vertebrates are found in the embryonic stage and it has been replaced by the mobile nervous tissue elements called the spinal cord in adults.
  
• There is a dorsal and hollow tubular nerve cord that runs along the length of the animal.
• Pharyngal gill slits are also observed in these animals in the embryonic stage.

So, the correct answer is option B.