**Core Concept**
Helminths are a class of parasitic worms that infect humans and other animals, causing a range of diseases. They are characterized by their complex body structure and ability to live in a variety of environments, including the human body.

**Why the Correct Answer is Right**
The correct answer will be a statement that accurately describes a characteristic of helminths. This might involve their life cycle, mode of transmission, or pathogenesis. Since the question asks for an exception, the correct answer will be a statement that does not apply to helminths.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because [insert reason]. Helminths are known to cause a range of diseases in humans, including schistosomiasis, filariasis, and hookworm disease.
**Option B:** This statement is incorrect because [insert reason]. Helminths are typically transmitted through fecal-oral contamination, skin contact, or vectors like mosquitoes and snails.
**Option C:** This statement is incorrect because [insert reason]. Helminths have complex life cycles that involve multiple hosts and stages, but they do not have a stage that is resistant to environmental changes.
**Option D:** This statement is incorrect because [insert reason]. Helminths are known to cause significant morbidity and mortality in humans, particularly in developing countries.

**Clinical Pearl / High-Yield Fact**
One key aspect of helminth infections is the development of immune responses that can lead to chronic inflammation and tissue damage. This is particularly relevant in the context of schistosomiasis, where chronic egg deposition can lead to fibrosis and bladder cancer.

**Correct Answer: D. Helminths do not cause significant morbidity and mortality in humans.**