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Which of the following characteristic features always holds true for the corresponding group of animals?
A
Viviparous – Mammalia
B
Possess a mouth with an upper and a lower jaw – Chordata
C
3-chambered heart with one incompletely divided ventricle – Reptilia
D
Cartilaginous endoskeleton – Chondrichthyes
Explanation
All Chondrichthyes have a cartilaginous endoskeleton; the other features have exceptions.
Detailed Solution
Animals of class Chondrichthyes are marine with a streamlined body. The mouth is ventral. Their endoskeleton is cartilaginous. The notochord is persistent throughout life. Gill slits are separate and without operculum.
So a cartilaginous endoskeleton always holds true for Chondrichthyes.
So a cartilaginous endoskeleton always holds true for Chondrichthyes.