**Core Concept**
The posterior urethra is a part of the male urethra, extending from the membranous urethra to the external urethral orifice. It is best visualized using imaging modalities that provide good visualization of the pelvic floor and surrounding structures.

**Why the Correct Answer is Right**
The posterior urethra is best visualized by **cystourethrography**, which involves the injection of a contrast agent into the bladder and urethra to visualize the posterior urethra and urethral strictures. This imaging modality provides detailed information about the urethral anatomy and can help diagnose conditions such as urethral stricture disease, urethral trauma, and urethral cancer. The use of cystourethrography allows for the visualization of the posterior urethra in relation to the surrounding pelvic floor structures, including the pubic bone, ischial rami, and external urethral sphincter.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **intravenous urography** (IVU) primarily visualizes the upper urinary tract, including the kidneys and renal pelvis, and is not ideal for visualizing the posterior urethra.
**Option B:** This option is incorrect because **magnetic resonance imaging (MRI)** of the pelvis can provide detailed information about the pelvic floor and surrounding structures, but it is not the best modality for specifically visualizing the posterior urethra.
**Option C:** This option is incorrect because **computed tomography (CT) urography** can provide detailed information about the upper and lower urinary tract, but it is not the best modality for specifically visualizing the posterior urethra.

**Clinical Pearl / High-Yield Fact**
When visualizing the posterior urethra, it is essential to remember that cystourethrography is the best modality for diagnosing urethral strictures and other conditions affecting the posterior urethra. This is because cystourethrography provides detailed information about the urethral anatomy and can help guide treatment decisions.

**Correct Answer:** C.