Select the appropriate option for a pouched mammal.

What do warm-blooded animals possess?

Which are exclusively viviparous?

$S$ - Statement: The duck-billed platypus is a mammal.
$R$ - Reason: Mammals are viviparous.

$A$: In metatherians,the scrotum is present in front of the penis.
$R$: In prototherians,the scrotum is present behind the penis.

Which pair of characters are found without exception in all mammals?