**Core Concept**
In a case of blunt abdominal trauma, the primary concern is to identify potential internal injuries that may not be immediately apparent. A hemodynamically stable patient allows for more comprehensive evaluation and diagnostic workup. The goal is to detect injuries that may not be evident on initial assessment and to guide further management.

**Why the Correct Answer is Right**
In a hemodynamically stable patient with blunt abdominal trauma, the next investigation of choice is a focused assessment with sonography for trauma (FAST) examination. This point-of-care ultrasound evaluates for free intraperitoneal fluid, which may indicate internal bleeding or organ injury. The FAST examination is particularly useful in detecting hemoperitoneum, which may be a sign of splenic or liver injury. The FAST exam is a rapid and non-invasive tool that can be performed at the bedside, making it an ideal initial investigation in this scenario.

**Why Each Wrong Option is Incorrect**
* **Option A:** CT scan of the abdomen is not the immediate next step in a hemodynamically stable patient. While it provides more detailed information, it is not as rapid or bedside-friendly as the FAST examination.
* **Option B:** Diagnostic peritoneal lavage (DPL) is an invasive procedure that is less commonly used nowadays, especially with the availability of FAST and CT scans. It carries a higher risk of complications compared to the FAST examination.
* **Option D:** Plain abdominal X-ray is not sensitive for detecting internal injuries and is not a suitable next step in the evaluation of blunt abdominal trauma.

**Clinical Pearl / High-Yield Fact**
In cases of blunt abdominal trauma, always consider the possibility of a hollow viscus injury (e.g., gastric or small bowel perforation) even if the FAST examination is negative. These injuries may not be immediately apparent on FAST and require a high index of suspicion.

**Correct Answer:** C