What is the subject in this simple sentence?

Egg-laying, pouched, and placental mammals are three subgroups of marsupials.

A.

Egg-laying

B.
mammals

C.
placental

D.
pouched

Question

What is the subject in this simple sentence? 

Egg-laying, pouched, and placental mammals are three subgroups of marsupials.
  
 
 

 
 

  

  A. 
 
Egg-laying
   
   

 
 

  

  B. 
  mammals   
   

 
 

  

  C. 
  placental   
   

 
 

  

  D. 
  pouched

aveline · Answer

Wrong section again...
Which answer is an example of a noun?

anonymous · Answer

not helpful

aveline · Answer

How are you confused?
@TWalker

thatawayz · Answer

the subject is mammals, its describing a few variations of mammals

thatawayz · Answer

egg laying mammals, pouched mammals and placental mammals