Which signs and symptoms of acute infection are related to the local inflammatory response triggered by the invading pathogen?

Choice A rationale Swelling (edema) and redness (erythema) are cardinal signs of localized acute inflammation. Redness results from vasodilation and increased blood flow to the injured site, while swelling is caused by increased capillary permeability, allowing fluid, proteins, and leukocytes to exude into the extravascular tissue space, a process known as exudation. Choice B rationale Fever (systemic elevation of body temperature, normal range 36.5°C-37.5°C or 97.7°F-99.5°F) and headache are generally considered systemic manifestations of infection, often resulting from the release of endogenous pyrogens like interleukins and tumor necrosis factor α into the circulation, acting on the hypothalamus's thermoregulatory center. Choice C rationale Weakness and malaise (a general feeling of discomfort, illness, or uneasiness) are non-specific systemic symptoms frequently associated with the body's overall response to systemic illness or infection, not specific indicators of the localized pathological changes occurring at the initial site of pathogen entry. Choice D rationale Nausea and anorexia (loss of appetite) are typically considered systemic or gastrointestinal symptoms of illness. They are mediated by systemic inflammatory mediators and hormonal changes, often reflecting the widespread physiological impact of the infection rather than the direct local response at the focus of inflammation.