**Core Concept**
Non-contrast computed tomography (CT) scan is the initial investigation of choice for subarachnoid hemorrhage (SAH) due to its high sensitivity for detecting blood in the subarachnoid space. SAH is a life-threatening condition that requires prompt diagnosis and treatment.

**Why the Correct Answer is Right**
The non-contrast CT scan is the preferred initial imaging modality for SAH because it can quickly identify blood in the subarachnoid space, which is a hallmark of this condition. The sensitivity of non-contrast CT scans for detecting SAH is particularly high in the first 48 hours after the hemorrhage. This is because blood in the subarachnoid space appears hyperdense on non-contrast CT scans, making it easily visible. The presence of blood in the subarachnoid space can also lead to changes in the surrounding brain tissue, which can be detected by non-contrast CT scans.

**Why Each Wrong Option is Incorrect**
* **Option A:** Lumbar puncture is not the initial investigation of choice for SAH because it is an invasive procedure that can be delayed and may not provide immediate results.
* **Option B:** Magnetic Resonance Imaging (MRI) is not the initial investigation of choice for SAH because it is a more time-consuming and expensive procedure than non-contrast CT scans, and may not be readily available in emergency situations.
* **Option D:** Angiography is not the initial investigation of choice for SAH because it is an invasive procedure that is typically reserved for patients who have undergone non-contrast CT scans and require further evaluation to determine the source of the hemorrhage.

**Clinical Pearl / High-Yield Fact**
In patients with SAH, it is essential to perform a non-contrast CT scan as soon as possible to determine the extent of the hemorrhage and to identify any potential complications, such as hydrocephalus or vasospasm.

**Correct Answer:** C.