In which of the following organisms, self-fertilization is seen?

Step-by-step solution

Fishes are chordates and roundworms belong to the phylum Aschelminthes. In these two organisms, the sexes are separate hence self-fertilization is not possible. Earthworms are hermaphrodite as both the sexes are present in the same body. Earthworms still do not show self-fertilization as the maturing times of both the sex organs are different. In earthworms, the male gonads mature earlier than female gonads. This is known as a protandry condition. Thus it shows cross-fertilization. In liver fluke both cross and sel