**Core Concept**
The management of alcohol withdrawal involves administering benzodiazepines to mitigate symptoms and prevent progression to severe withdrawal. A loading dose of diazepam is given to rapidly achieve therapeutic levels, reducing the severity of withdrawal symptoms.

**Why the Correct Answer is Right**
The loading dose of diazepam for alcohol withdrawal is typically 20 mg. This initial dose is administered to rapidly increase the plasma concentration of diazepam, thereby reducing the severity of withdrawal symptoms such as tremors, agitation, and seizures. The rapid onset of action of diazepam is due to its high lipid solubility, which allows it to cross the blood-brain barrier quickly.

**Why Each Wrong Option is Incorrect**
**Option A:** 10 mg is an insufficient dose to effectively manage severe alcohol withdrawal symptoms, and may lead to inadequate sedation.
**Option B:** 30 mg is excessive and may cause respiratory depression, a potentially life-threatening side effect.
**Option C:** 15 mg is a suboptimal dose that may not provide sufficient relief from withdrawal symptoms.

**Clinical Pearl / High-Yield Fact**
When administering a loading dose of diazepam for alcohol withdrawal, the initial dose should be 20 mg, and subsequent doses should be titrated based on clinical response and vital signs.

**Correct Answer: A. 20 mg.**