**Core Concept**
In cases of blunt abdominal trauma, the primary goal is to identify any potential life-threatening injuries, such as bleeding or organ damage, while minimizing further risk to the patient. The chosen investigation must be able to accurately assess the extent of injury without causing additional harm.

**Why the Correct Answer is Right**
Contrast-Enhanced Computed Tomography (CECT) of the abdomen is the preferred imaging modality for blunt abdominal trauma due to its high sensitivity and specificity in detecting injuries, particularly in the solid organs and vascular structures. The use of intravenous contrast allows for better visualization of the bowel, liver, spleen, and kidneys, enabling the detection of subtle injuries that may not be apparent on non-contrast CT scans. Additionally, CECT can be performed quickly, allowing for timely intervention if necessary.

**Why Each Wrong Option is Incorrect**
* **Option B:** MRI abdomen is not typically used in acute blunt abdominal trauma as it is time-consuming, not readily available, and not suitable for patients with potential bleeding or vascular injuries.
* **Option C:** Diagnostic Peritoneal Lavage (DPL) is an invasive procedure that involves inserting a catheter into the peritoneal cavity to check for blood or other fluid. While it can be useful in certain situations, it is not the first-line investigation for blunt abdominal trauma due to its invasive nature and lower sensitivity compared to CECT.
* **Option D:** Focused Assessment with Sonography for Trauma (FAST) is a bedside ultrasound examination that can quickly identify free fluid in the abdominal cavity, suggesting bleeding or other injuries. However, it has limitations in detecting solid organ injuries and is not as sensitive as CECT for evaluating the extent of trauma.

**Clinical Pearl / High-Yield Fact**
In cases of blunt abdominal trauma, it is essential to remember that CECT should not be delayed if there is a high suspicion of significant injury, as this can lead to worsening of the patient's condition. A "damage control" approach, involving immediate surgical intervention and stabilization, may be necessary in such cases.

**✓ Correct Answer: A. CECT abdomen**