Monotremes are mammals that reproduce by laying eggs.
Like the platypus, an echidna is an egg laying mammal.
Platypus are monotremes.
A platypus is an example of 
Options:
  - a reptile
  - animals
  - an amphibian
  - a monotreme
  - killing insects
  - insects
  - murmur
  - an arachnid