## Core Concept
The question tests the understanding of the autonomic nervous system's control over bladder function, specifically focusing on the role of α-adrenergic receptors. α-adrenergic receptors are part of the sympathetic nervous system and play a crucial role in the contraction and relaxation of smooth muscle in various parts of the body, including the bladder.

## Why the Correct Answer is Right
Stimulation of α-adrenergic receptors in the bladder primarily affects the smooth muscle of the bladder neck and the prostate (in males), leading to contraction. This contraction increases the resistance to the flow of urine, effectively promoting urine storage by making it harder for urine to leave the bladder. The main effect relevant to the bladder is the contraction of the internal urethral sphincter and prostatic smooth muscle, which helps in urine retention.

## Why Each Wrong Option is Incorrect
- **Option A:** Incorrect because α-adrenergic receptor stimulation does not directly cause relaxation of the detrusor muscle of the bladder; instead, it influences the bladder neck and urethral sphincter.
- **Option B:** Incorrect because while contraction of the detrusor muscle is crucial for urination, α-adrenergic receptors primarily influence the bladder neck and prostate, not directly causing detrusor contraction.
- **Option C:** Incorrect because the primary effect of α-adrenergic stimulation is not the relaxation of the internal urethral sphincter; rather, it causes contraction, which aids in urine retention.

## Clinical Pearl / High-Yield Fact
A key point to remember is that α-adrenergic blockers (e.g., alfuzosin, tamsulosin) are used to treat benign prostatic hyperplasia (BPH) symptoms by relaxing the smooth muscle in the prostate and bladder neck, improving urine flow. This highlights the clinical relevance of α-adrenergic receptors in bladder and prostate function.

## Correct Answer Line
**Correct Answer: D.**