Ans. is 'd' i.e., FlukeTrematodes (fluke)o These are flat, leaf like helminths.o They can be classified depending on their site of localization in human tissues.Blood flukesVesical venous plexus: Schistosoma hematobium.Rectal venous plexus & portal venous system : S mansoni (inferior mesentric vein), S japonicum (superior mesenteric vein).Intestinal flukesSmall intestine : Fasciola buski, Heterophyes heterophes, Metagonimus vokogawi, Watsonius watsoni.Large intestine : Gastrodiscoides hominis.Tissue flukesLiver flukes : Fasciola hepatica, Clonorchis sinensis, Opisthorchis felineus, O viverrini.Lung fluke : Paragonimus westermani.o Trematodes are monoecious (hermaphrodite), i.e. sexes are not separate. One exception being Schistosomes, which are diecious with separate sexes.o Trematodes complete their life cycle in three hosts: One definitive (man) and two intermediate hosts (Freshwater snail or mollusc as first intermediate host and fish or crab as second intermediate host),o Trematodes are Oviparous and lay operculated eggs, except for schistosomes which lay non-operculated eggs.Metazoa (Helminths)NemathelminthesPlatyhelminthes ||||Class : Nemafoda(Roundworms)Class : Cestoda(Tapeworms)Class: Trematoda(Flukes)||||||||Intestinal speciesIntestinal-tissue speciesBlood-tissue speciesIntestinal speceisIntestinal-tissue speciesIntestinal speciesBlood speciesTissue species1. Enterobius vermicularisl. Triehinella spiralis1. Wuchereria bancrofti1. Taenia sagnata1. Echinococcus granulosus1. Fasciolo- psis buski1. Schis- tosoma species1. Fasciola hapatic (liver fluke)2. Trichura trichisis2. Dracunculus medinensis2. Brutgia malayi2. Taenia solium 3. Ascaris lumbricoides 3. Loa toa4. Onchocerca3. Hvmenolepsis nana 2. Parago- nimus wester-mni (lung fluke)4. Necator americanus volvulus4. Diphyllobothrium latum 5. Ancylotoma duodenalc 6. Strongyloide stercoraliss