What are warm-blooded animals called?

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 $Oryctolagus$?

Elephants have very poor

Assertion $(A)$: Cold-blooded animals do not have a fat layer.
Reason $(R)$: Cold-blooded animals use their fat for metabolic processes during hibernation.

The characteristic feature of Eutherians is ......

Which one of the following is an exclusive character of class Mammalia?