The tusk of an elephant is an enormously enlarged:

Note the following:
$I.$ Dentition is heterodont.
$II.$ Canines are poorly developed.
$III.$ Incisors are chisel-like,poorly developed.
$IV.$ Herbivorous and diastema is present.
$V.$ The dental formula is $I \frac{2}{1}, C \frac{0}{0}, P m \frac{3}{2}, M \frac{3}{3}$.
Which of the above are true for $Oryctolagus$?

Which of the following is a prototherian mammal?

All mammals without any exception are characterized by

Which one of the following characters is not typical of the class $Mammalia$?

The external ear (pinna) is a characteristic feature of: