The only poisonous mammal is:

Which of the following is an oviparous mammal?

Which of the following is the largest mammal?

Which group of animals possesses a marsupium?

Which of the following is the fastest running mammal?

$A$: The duck-billed platypus and the spiny ant-eater,both are egg-laying animals yet are grouped under mammals.
$R$: Both of them have seven cervical vertebrae and mammary glands without teats.