Which of the following statements is true about helminths?

The statement that some helminths are monoecious is true because certain helminths, particularly within the class Trematoda (flukes) and the class Cestoidea (tapeworms), possess both male and female reproductive organs in the same individual. This allows these organisms to potentially self-fertilize or mate with others. In contrast, there are also dioecious helminths, meaning that they have separate sexes, such as many species of roundworms (Nematoda). Understanding the reproductive strategies of helminths is crucial in the study of their life cycles and how they infect hosts.

The claim that all helminths have separate sexes is not accurate as it overlooks the monoecious forms. The notion that helminths do not reproduce is incorrect because they are well-known for their various reproductive strategies, which include both sexual and asexual reproduction depending on the species. Lastly, saying that all helminths have a complete digestive system is misleading as many species, especially tapeworms, lack a digestive system entirely and absorb nutrients directly through their tegument. Thus, the correct response highlights the diversity of reproductive strategies among helminths, emphasizing the existence of monoecious forms as a distinct characteristic.