Question

All mammals without any exception, are characterised by

• A. Viviparity and biconcave red blood cells.
• B. Extra-abdominal testes and a four-chambered heart.
• C. Heterodant teeth and 12 pairs of cranial nerves.
• D. A muscular diaphragm and milk producing glands.

Answer 1

The correct option is D A muscular diaphragm and milk producing glands.

Vivipary is shown by all mammals except monotremes (Platypus and echidna)

All mammals do not have Biconcave RBCs, example Camel has ovaloid RBCs.

Elephants do not have extra abdominal testes and four-chambered hearts are not exclusive to Mammals.

Heterodont teeth and 12 cranial nerves are both not exclusive to mammals as they can be found in other animal groups too.

Muscular diaphragm and mammary glands are the only characteristics having no exceptions and are exclusive to mammals.

So the correct answer is 'A muscular diaphragm and milk-producing glands'.