Class 11 NEET Biology Animal Kingdom Questions Part 3

Option (1) is correct answer because presence of hairs, pinna and mammary glands are unique features of mammals.
Options (2), (3) and (4) are not correct because, monocondylic skull is present in reptiles and aves whereas mammals have dicondylic skull. Tympanic membrane is present in amphibians also, so it is not considered as unique feature.
Indirect development is not seen in mammals.