Respuesta :
Answer:
based on how their embryos develop
Explanation:
Mammals are further classified into three types: placental, marsupial, and monotreme.
Also, I just took the quiz and I got it right, mate :)
The criteria used to classify mammals into groups is the presence of hairs.
Mammals:
They are the animals who have mammary gland mean the mother feeds the milk to their newborn.
One unique characteristics of the mammal is that they have have hair in at least one stage of their development.
No other animals like reptiles or birds have true hairs.
To know more about Mammals,
https://brainly.com/question/10194338