**Core Concept**
The zona glomerulosa is the outermost layer of the adrenal cortex, responsible for producing hormones that regulate electrolyte balance and blood pressure. It is one of the three distinct zones of the adrenal cortex, each with distinct functions and hormone secretion profiles.

**Why the Correct Answer is Right**
The zona glomerulosa secretes aldosterone, a mineralocorticoid hormone that plays a crucial role in regulating sodium and potassium levels in the body. Aldosterone stimulates the kidneys to reabsorb sodium ions and excrete potassium ions, leading to increased blood pressure and volume. The secretion of aldosterone is primarily regulated by the renin-angiotensin-aldosterone system (RAAS), which responds to changes in blood pressure and volume.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because the zona glomerulosa does not secrete cortisol, which is produced by the zona fasciculata. Cortisol has a wide range of effects on metabolism, immune response, and stress response.

**Option B:**
This option is incorrect because the zona glomerulosa does not secrete androgens, which are produced by the zona reticularis. Androgens, such as dehydroepiandrosterone (DHEA), play a role in the development of male characteristics and secondary sex traits.

**Option C:**
This option is incorrect because the zona glomerulosa does not secrete ACTH, which is actually produced by the anterior pituitary gland. ACTH stimulates the adrenal cortex to produce cortisol and other hormones, but it is not secreted by the zona glomerulosa itself.

**Clinical Pearl / High-Yield Fact**
The zona glomerulosa is sensitive to potassium levels, and hyperkalemia can stimulate the secretion of aldosterone. This is why patients with primary aldosteronism (Conn's syndrome) often present with hypokalemia, despite the excessive secretion of aldosterone.

**Correct Answer: D. Aldosterone.**