**Core Concept**
Pheochromocytoma is a rare tumor of the adrenal gland that secretes excessive amounts of **catecholamines**, leading to various clinical manifestations. The primary **catecholamines** involved are **epinephrine** (adrenaline), **norepinephrine** (noradrenaline), and **dopamine**.

**Why the Correct Answer is Right**
The correct answer is related to the predominant secretion of pheochromocytoma. **Norepinephrine** is the primary catecholamine secreted by most pheochromocytomas, although some tumors may secrete **epinephrine** or both. The secretion of these hormones leads to symptoms such as hypertension, tachycardia, and sweating.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because, although **epinephrine** is a catecholamine secreted by pheochromocytoma, it is not the predominant one.
**Option C:** Incorrect as **dopamine** is also secreted but not the primary hormone.
**Option D:** This option is not provided, but it would be incorrect if it does not correspond to the correct hormone.

**Clinical Pearl / High-Yield Fact**
Pheochromocytomas are known for their classic triad of symptoms: headache, sweating, and palpitations, primarily due to the excessive secretion of **catecholamines**.

**Correct Answer:** D. Norepinephrine