## Core Concept
Angiofibroma, typically referred to as juvenile nasopharyngeal angiofibroma (JNA), is a highly vascular tumor that primarily affects adolescent males. The investigation of choice for diagnosing and evaluating the extent of angiofibroma involves imaging techniques that can accurately delineate its vascular nature and extent.

## Why the Correct Answer is Right
The correct answer, **CT Angiography**, is the investigation of choice for angiofibroma because it provides detailed images of the tumor's vascular structure and its relationship with surrounding anatomical structures. CT angiography helps in identifying the tumor's blood supply, which is crucial for surgical planning. It is particularly useful in showing the characteristic features of JNA, such as its location in the nasopharynx, extension into surrounding areas, and its intense vascularity.

## Why Each Wrong Option is Incorrect
- **Option A: Ultrasound** - While ultrasound can provide information on blood flow and may detect the tumor, it is limited by its inability to provide detailed images of complex anatomical areas like the nasopharynx and surrounding structures.
- **Option B: MRI** - MRI is useful for soft tissue characterization and can show the extent of the tumor. However, it may not be as effective as CT angiography in demonstrating the tumor's vascularity and its relationship with bony structures.
- **Option D: Plain X-ray** - Plain X-ray can show some features suggestive of angiofibroma, such as a nasopharyngeal mass or bony destruction, but it does not provide detailed information on the tumor's extent or vascularity.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that **juvenile nasopharyngeal angiofibroma (JNA) is highly vascular and predominantly affects adolescent males**. CT angiography not only aids in diagnosis but also in preoperative embolization, which is often performed to reduce intraoperative bleeding.

## Correct Answer: C. CT Angiography