Substrate Concentration I believe
Answer:
a. Mammalia
Explanation:
Mammalia are the class species that have distinct systems and separate ducts for different activities like reproduction, excretory, and defecatory and moreover they have nipples to feed their young ones.
So, the above species which has a single duct for reproductive, excretory, and defecatory material as well as a lack of true nipples does not belong to Mammalia
The answer for your question is preganent
