You discover a new species and are given the task of describing and classifying it. upon closer examination, you find that it has a single duct for reproductive, excretory, and defecatory material as well as a lack of true nipples. which group are you sure this species does not belong to?
a. mammalia
b. metatheria
c. prototheria
d. synapsida

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

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.