The monotremata are named so because they have a single opening for;

Correct option is D

The correct answer is Urination, defecation and reproduction.
· Monotremes (e.g., platypus, echidna) have a cloaca, a single opening for excretion and reproduction.
· The name “monotreme” means “one hole.”
· They are egg-laying mammals.
· Other mammals have separate openings.
Information Booster:
· Monotremes are primitive mammals found in Australia and New Guinea.
· They lay leathery eggs but produce milk.
· Lack nipples; milk is secreted on skin.
· Provide evolutionary link between reptiles and mammals.