The correct option is B Ornithorhynchus
Majority of mammals are viviparous and give birth to young ones. But there are a few exceptions. These are the egg-laying mammals. They are oviparous and lay eggs.
Eg: Ornithorhynchus (Platypus).
Macropus is Kangaroo. Delphinus is the common dolphin. Equus is the genus of horse and donkey.
Macropus, Delphinus, Equus are viviparous and give birth to young ones.