**Core Concept**
The most sensitive investigation for abdominal trauma in a hemodynamically stable patient involves imaging techniques that can accurately detect injuries to internal organs, such as the liver, spleen, and intestines. This requires a modality that can provide high-resolution images of the abdominal cavity, including the solid organs and vascular structures.

**Why the Correct Answer is Right**
CT scans are the gold standard for imaging abdominal trauma due to their high sensitivity and specificity in detecting injuries. This is because CT scans can provide detailed images of the abdominal cavity, including the solid organs, vascular structures, and soft tissues. The use of contrast agents can further enhance the visualization of vascular injuries and bleeding. The multiplanar reconstruction capabilities of CT scans allow for accurate assessment of organ injuries, such as liver lacerations or splenic hematomas.

**Why Each Wrong Option is Incorrect**
* **Option B:** Ultrasonography is less sensitive than CT scans for detecting abdominal injuries, particularly in patients with complex or subtle injuries. While ultrasonography can be useful for rapid assessment, it is not as reliable as CT scans for definitive diagnosis.
* **Option C:** Diagnostic peritoneal lavage (DPL) is a sensitive test for detecting bleeding into the peritoneal cavity but is less specific than CT scans for identifying the source of bleeding. DPL is often used as a triage tool in unstable patients, but it is not the most sensitive investigation for abdominal trauma in a hemodynamically stable patient.
* **Option D:** MRI is not typically used for initial evaluation of abdominal trauma due to its limited availability, longer scan times, and higher costs compared to CT scans. While MRI can provide detailed images of soft tissues, it is not the most sensitive investigation for detecting injuries to solid organs and vascular structures.

**Clinical Pearl / High-Yield Fact**
When evaluating abdominal trauma, it is essential to consider the patient's hemodynamic stability and the availability of imaging modalities. In hemodynamically unstable patients, ultrasonography or diagnostic peritoneal lavage may be used as a rapid assessment tool, while CT scans are typically reserved for stable patients who require more detailed imaging.

**✓ Correct Answer: A. CT Scan**