**Core Concept**
The question describes a clinical scenario involving a 2-week-old baby with scrotal pigmentation, hyponatremia, hypoglycemia, and hyperkalemia, which suggests a metabolic disorder. The key concept here is the association of congenital adrenal hyperplasia (CAH) with salt-wasting crisis, which can lead to hypotension, shock, and electrolyte imbalances.

**Why the Correct Answer is Right**
The correct answer is related to 21-hydroxylase deficiency, a form of CAH that leads to impaired cortisol and aldosterone production. This results in a salt-wasting crisis, characterized by hyponatremia, hypoglycemia, and hyperkalemia due to the lack of aldosterone-mediated sodium retention and potassium excretion. The scrotal pigmentation is a result of excess androgen production.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because 17-hydroxylase deficiency is associated with hypertension, hypokalemia, and hyporeninemic hypoaldosteronism, which does not match the clinical scenario described.
* **Option B:** This option is incorrect because 11-beta-hydroxylase deficiency is associated with hypertension, hypokalemia, and virilization due to excess androgen production, which does not match the clinical scenario described.
* **Option C:** This option is incorrect because 3-beta-hydroxysteroid dehydrogenase deficiency is a rare form of CAH that presents with a more severe phenotype, including mineralocorticoid deficiency and salt-wasting, but it is not the most common form of CAH.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that CAH is a common cause of neonatal salt-wasting crisis, which can be life-threatening if not promptly treated. The clinical presentation of CAH can vary depending on the enzyme deficiency, but the presence of scrotal pigmentation and electrolyte imbalances should raise suspicion for this condition.

**Correct Answer: D. 21-hydroxylase deficiency**