Okay, let's tackle this question. The question is asking which method best visualizes the posterior urethra. First, I need to recall the anatomy of the urethra. The urethra has two parts: the anterior and posterior. The posterior urethra includes the prostatic and membranous portions, while the anterior is the spongy part.

Now, the options aren't listed, but the correct answer is likely a specific imaging technique. Common methods include retrograde urethrography, cystoscopy, ultrasound, or MRI. Retrograde urethrography is often used for posterior urethral visualization. It involves injecting contrast into the urethra under pressure to outline the posterior parts. Cystoscopy, especially with a rigid scope, allows direct visualization but might be more invasive. MRI could show the surrounding structures but might not be the best for the urethral lumen itself. Ultrasound, particularly endourethral, could be an option but maybe less standard.

Wait, the correct answer here is probably retrograde urethrography. Let me confirm. The posterior urethra is best seen with retrograde urethrography because it's designed to visualize the prostatic and membranous segments. Cystoscopy allows direct view but is more invasive. So the answer is A if that's the option given. But without the options, I have to assume based on standard knowledge. The key point is that retrograde urethrography is the gold standard for posterior urethra assessment, especially in trauma cases like urethral strictures or fractures.

**Core Concept**
The posterior urethra (prostatic and membranous segments) is best visualized using imaging techniques that provide high-resolution anatomical detail. Retrograde urethrography is the gold standard for evaluating posterior urethral integrity, particularly in trauma or stricture.

**Why the Correct Answer is Right**
**Retrograde urethrography** involves injecting contrast retrograde through the urethra under fluoroscopy. It directly outlines the posterior urethra, allowing assessment of strictures, diverticula, or trauma. The contrast fills the prostatic and membranous urethra under pressure, making it superior to other methods for posterior visualization. It is preferred over antegrade approaches for posterior pathologies.

**Why Each Wrong Option is Incorrect**
**Option A:** *Ultrasonography* lacks resolution for the posterior urethra and is better for renal or bladder imaging.
**Option B:** *CT urography* provides cross-sectional anatomy but does not dynamically visualize the urethral lumen.
**Option C:** *Cystoscopy* visualizes the anterior urethra and bladder but is limited for the membranous segment due to its location in the pelvic floor.

**Clinical Pearl / High-Yield Fact**
Retrograde urethrography is the **first-line diagnostic test** for posterior urethral injuries (e.g., pelvic fractures). Remember: **"Posterior urethra = retrograde urethrogram"** to avoid confusing with antegrade pyelography.

**Correct Answer: A. Retrograde urethrography**

✓ Correct Answer: C. Voiding cystogram