Classification of animals is based on their specific characters and unique characters. Kingdom Animalia is broadly classified into two phylum Invertebrates and Vertebrates. A phylum Vertebrata is further subdivided into 5 class namely Pisces, Amphibians, Reptiles, Birds, and Mammals. Class Mammalia is further sub-divided into 3 sub-classes are Prototheria, Metatheria, and Eutheria.Complete answer:
All the mammals have the presence of mammary glands but based on a few notable differences this class is subdivided into 3 sub-classes Prototheria, Metatheria, and Eutheria.
Prototheria are egg-laying mammals. Examples: Platypus, Echidna
. Metatheria includes pouch bearing mammal Examples: Kangaroo, Opossum. Eutheria includes mammals having placenta, for example Humans, Bats.
So, Hence the correct answer is option B-Metatheria. The presence of a double vagina and double the uterus is a characteristic feature of mammalian subclass Metatheria.Note:
| They are oviparous animals.(produce young ones by laying eggs)||They are viviparous animals.(produce young ones by live birth)||They are viviparous animals.(produce young ones by live birth)|
| The ears lack pinna.||They have ear pinna. ||They have ear pinna aquatic forms that are an exception to this.|
|Vagina and uterus are absent.||Double vagina and double uterus present.||One vagina and one uterus present.|
|Nipples are absent on the mammary gland.||Nipples are present.||Nipples are present.|
Bat is the only flying mammal that is often misunderstood as a bird. Sub-class prototheria has only one living order monotreme with just five living species. Marsupials are pouch bearing mammals, pouches are meant for young ones' development. Eutherians have a placenta meant for providing oxygen and nutrients to the growing embryo. Placenta also helps in the removal of waste from a foetus's body.