## **Core Concept**
The patient's presentation suggests shock, likely due to hypovolemia from internal bleeding, and abdominal distension which could indicate internal abdominal injury or bleeding. In trauma settings, especially with signs of shock and abdominal involvement, rapid assessment and diagnosis are critical.

## **Why the Correct Answer is Right**
The correct answer, **Focused Assessment with Sonography for Trauma (FAST)**, is appropriate in this scenario because it is a quick, bedside ultrasound examination that can help identify free intraperitoneal fluid (which could indicate bleeding) and pericardial effusion. It's particularly useful in unstable patients where moving to CT scan might not be feasible. FAST can be performed rapidly, does not interfere with resuscitative efforts, and helps in making immediate surgical decisions.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While an X-ray can provide some information, it's not the best initial choice for assessing abdominal trauma with suspicion of internal bleeding or organ injury. It's less sensitive for detecting free fluid or specific organ injuries compared to FAST or CT.
- **Option B:** A CT scan provides detailed images and is highly sensitive for detecting injuries. However, it may require moving the patient, administering contrast, and exposes the patient to radiation. It's not the immediate first step in an unstable patient.
- **Option C:** This seems to be a placeholder and does not provide a recognizable diagnostic test or investigation.

## **Clinical Pearl / High-Yield Fact**
In trauma patients with suspected abdominal injury and hemodynamic instability, the priority is to quickly identify life-threatening conditions that require immediate intervention, such as surgical exploration. The **FAST exam** is a valuable tool because it's quick, non-invasive, and can be done simultaneously with resuscitative efforts.

## **Correct Answer:** . **Focused Assessment with Sonography for Trauma (FAST)**