The correct option is B Plasmodium
Plasmodium is an obligate intracellular parasite with a complex life cycle involving both an invertebrate and a vertebrate host. It causes malaria.
Ancylostoma is a roundworm and a parasite in human intestines. It is an extracellular parasite.
Trichomonas vaginalis is an extracellular protist parasite. It causes trichomoniasis in both males and females.
Mosquito acts as a vector for various diseases like malaria, dengue, etc.