Okay, let's tackle this question. The user is asking about the investigation of choice for a patient with abdominal trauma who's hemodynamically stable. First, I need to recall the core concept here. Abdominal trauma can be blunt or penetrating. The key is determining the best imaging modality. For stable patients, the gold standard is usually CT scan, right? Because it's more sensitive and specific than other methods like ultrasound.

So the correct answer is likely CT of the abdomen with contrast. Now, the options aren't listed, but common wrong answers might include things like plain X-ray, ultrasound, or even exploratory laparotomy. Let me think about each option.

The core concept is about choosing the right imaging modality. The patient is stable, so they don't need immediate surgery. CT is preferred because it can detect solid organ injuries and free fluid. Ultrasound, like FAST exam, is quick but less detailed. Exploratory laparotomy is for unstable patients.

For the wrong options: Option A might be plain X-ray, which isn't useful here. Option B could be ultrasound, which is a good initial screen but not the best choice. Option C might be MRI, which is not typically used in trauma. Option D could be exploratory laparotomy.

Clinical pearl: Remember that CT is the investigation of choice for stable patients. For unstable ones, go straight to surgery. Also, FAST is a bedside tool but not enough on its own.

Need to make sure the explanation is concise, covers all sections, and fits the character limit. Avoid jargon but use precise terms. Check that each wrong answer is addressed properly. Alright, time to structure the explanation accordingly.

**Core Concept**
In hemodynamically stable patients with suspected abdominal trauma, the **CT scan of the abdomen and pelvis with intravenous contrast** is the preferred diagnostic modality. It provides detailed visualization of solid organs, hollow viscera, and retroperitoneal structures, allowing accurate detection of injuries like splenic lacerations, hepatic tears, and intraperitoneal hemorrhage. Stability permits non-urgent imaging, maximizing diagnostic yield.

**Why the Correct Answer is Right**
CT scanning is superior to other modalities due to its high sensitivity (95–98%) and specificity (90–95%) for intra-abdominal injuries. Contrast enhancement helps identify active bleeding (e.g., "blush" sign) and vascular injuries. It replaces older methods like plain X-rays or peritoneal lavage and avoids unnecessary surgery in stable patients. The absence of hemodynamic instability allows time for this comprehensive evaluation.

**Why Each Wrong Option is Incorrect**
**Option A:** Plain abdominal X-ray is insensitive for visceral injuries and only detects free air or gross hemorrhage.
**Option B:** FAST (Focused Assessment with Sonography for Trauma) is a rapid ultrasound tool but lacks sensitivity for retroperitoneal or pancreatic injuries.
**Option C:** MRI is not used in acute trauma due to cost, time constraints, and limited availability.
**Option D:** Exploratory laparotomy is reserved for hemodynamically unstable patients where imaging is contraindicated.

**Clinical Pearl / High-Yield Fact**
Remember the **"Golden Hour"** concept: stable trauma patients benefit from CT to avoid unnecessary surgeries. FAST is a **screening tool**,

✓ Correct Answer: A. FAST