The correct option is A Fasciola
In Fasciola, asexual reproduction by germ cells of sporocyst and redia is followed by sexual reproduction in the adult stage. This is 'alternation of generation' in the life cycle of Fasciola where they complete its life cycle in two alternating hosts. Sheep is the primary definitive host and the secondary host is a freshwater snail.
Thus, the correct answer is option B.