The lower jaw of a mammal is made up of:

Thecodont teeth are present in:
$a.$ Sphenodon
$b.$ Crocodiles
$c.$ Mammals
$d.$ Scoliodon

Bats are included in the same taxonomic class as.....

Which of the following is a characteristic of all mammals without any exception?

Assertion : The duck-billed Platypus and the spiny ant-eater,both are egg-laying animals yet they are grouped under mammals.
Reason : Both of them have seven cervical vertebrae and $12$ pairs of cranial nerves.

Choose the correct option for the following statements:
$(i)$ Animals that maintain a constant body temperature are called $cold-blooded$ / $warm-blooded$ animals.
$(ii)$ Mammals are $viviparous$ / $oviparous$ animals.