Answer :
Platypus is an oviparous.
It is mammal that lay eggs and are called prototherian.
Oviparous animals are that type of species that lay eggs, with little or total absence of embryonicdevelopment within the body of mother.
This is the methodology as well as reproductive practice of fish, amphibians, reptiles, all birds, and the monotremes.
As per convension, insects, molluscs, and arachnids are reported as oviparous.