Answer:
d) monotremes secrete milk through pores on the surface of the mother's abdomen
Step-by-step explanation:
Monotremes are a specific group of egg-laying mammals (oviparous). They do not give birth to their young ones like other mammals. Thus, other mammals are viviparous. Although monotremes lay eggs but like other mammals secrete milk through mammary gland openings in the skin. Examples of monotremes are echidna and the duck-billed platypus.