Biology · ANIMAL KINGDOM

Both Aves (birds) and Mammalia (mammals) belong to higher vertebrates. Which of the following sets contains ONLY those characters that are shared by BOTH Aves and Mammalia, without any exception?

1. A
   Homoiothermy, four-chambered heart, internal fertilisation, and respiration by lungs.
2. B
   Presence of pneumatic bones, air sacs supplementing respiration, and homoiothermy.
3. C
   Presence of external ear pinnae, mammary glands, and internal fertilisation.
4. D
   Presence of epidermal hair, viviparity, and four-chambered heart.