Final answer:
Florence Nightingale's theoretical assumptions about nursing and healthcare highlighted the importance of environmental factors on health, rather than genetics alone, static conditions, or lack of hygiene.
Step-by-step explanation:
Florence Nightingale's theoretical assumptions were about nursing and healthcare is B) Health is influenced by environmental factors. According to Nightingale's observations and subsequent reforms during the Crimean War, she posited that environmental conditions such as sanitation and access to hospital facilities had significant impacts on the health and mortality rates of soldiers.
Nightingale's findings are congruent with modern understanding that health outcomes are not static but are greatly affected by a variety of factors including lifestyle, environmental conditions, and personal hygiene. Her work predates the germ theory of disease, emphasizing that cleanliness plays an important role in preventing illness—a stark contrast to the incorrect assumptions that health is unrelated to hygiene (C) and that health is static and unchangeable (D). Additionally, her approach contradicts the idea that health is solely determined by genetics (A), as she demonstrates the importance of external conditions in health and disease.