## Core Concept
Trematodes, also known as flukes, are a class of flatworms that are parasitic to humans and other animals. They have a complex life cycle involving multiple hosts, typically including a definitive host where they reach sexual maturity and one or more intermediate hosts where they undergo asexual reproduction. Understanding their life cycle, morphology, and characteristics is crucial for diagnosing and managing infections.

## Why the Correct Answer is Right
The correct answer, although not directly provided, requires an understanding of specific characteristics or examples of trematodes that do not fit with the general truths about this class of parasites. Typically, trematodes are known for having a specific body structure, life cycle, and for causing particular diseases in humans.

## Why Each Wrong Option is Incorrect
- **Option A:** Without specific details on what Option A states, we can infer that if it's a characteristic of trematodes (e.g., having a flattened body, being hermaphroditic except for certain species, having a specific life cycle involving hosts), then it would be true and not the correct answer to the question about which statement is not true.
- **Option B:** Similarly, if Option B describes a true feature of trematodes, it would not be the correct answer to this question.
- **Option C:** This option would also be incorrect if it accurately describes a feature or aspect of trematodes.
- **Option D:** This is stated as the correct answer but without context, we know that if an option does not accurately describe a feature of trematodes, it would be the one that stands out as not belonging.

## Clinical Pearl / High-Yield Fact
A key point to remember is that trematodes include species like *Schistosoma* spp., which cause schistosomiasis, and *Clonorchis sinensis*, which can lead to clonorchiasis. These parasites have complex life cycles and can cause significant morbidity in infected individuals. Recognizing their life cycles and the diseases they cause is crucial for diagnosis and treatment.

## Correct Answer: D.