**Core Concept**
The question is testing the clinical knowledge of fat embolism syndrome (FES), a complication that can occur after long bone fractures, particularly of the femur. FES is characterized by the release of fat globules into the bloodstream, which can lead to respiratory and cardiovascular complications.

**Why the Correct Answer is Right**
Fat embolism syndrome typically presents 24-72 hours after the initial injury, with symptoms including dyspnea, chest pain, and hemoptysis. The condition occurs when fat globules from the bone marrow enter the systemic circulation, causing a blockage in the pulmonary arteries. This leads to hypoxemia, which in turn triggers a cascade of physiological responses, including the release of various inflammatory mediators. The correct answer is related to the pathophysiology of FES.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not relate to the clinical presentation of FES. The symptoms described in the question are specific to FES and do not match the presentation of this condition.

**Option B:** This option is incorrect as it is not directly related to the pathophysiology of FES. While inflammation is a component of the condition, it is not the primary cause of the symptoms described.

**Option C:** This option is incorrect as it is a potential complication of other conditions, such as pulmonary embolism or pneumonia, but not specifically related to FES.

**Option D:** This option is incorrect as it is a potential cause of hypotension, but not the primary cause of the symptoms described in the question.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of FES is the presence of petechial rash, which can be seen in up to 90% of patients. This is due to the microemboli of fat globules that cause damage to the capillary walls, leading to bleeding into the skin.

**Correct Answer:** D. Fat embolism syndrome is a well-known complication of long bone fractures, particularly of the femur.