The correct option is B Duck-billed platypus, Oviparous, Mammalia
Millipede and Silverfish have jointed legs as well as ventral nerve cord and thus, belongs to Arthropoda.
Sea anemone is a cnidarian and cnidarians are diploblastic.
The duck-billed platypus is an egg-laying (oviparous) mammal.
Thus, the correct answer is option B.