**Core Concept**
The question is testing the student's knowledge of the pharmacological classification of drugs used to treat various conditions. In this case, the focus is on selective alpha-2 (α2) adrenergic receptor antagonists. These receptors are part of the autonomic nervous system and play a crucial role in regulating blood pressure, heart rate, and other physiological processes.

**Why the Correct Answer is Right**
Selective α2 adrenergic receptor antagonists block the action of α2 receptors, leading to an increase in sympathetic tone. This results in increased release of norepinephrine from the nerve terminals, increasing heart rate, cardiac contractility, and vascular tone. The correct answer is an example of a drug that selectively blocks α2 receptors, promoting these effects.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it's a non-selective α blocker, which blocks both α1 and α2 receptors. Non-selective α blockers have a broader range of effects, including vasodilation and decreased blood pressure.
**Option B:** This option is incorrect as it's a selective α1 receptor blocker, which primarily causes vasodilation and decreased blood pressure without the significant increase in sympathetic tone seen with α2 antagonism.
**Option C:** This option is incorrect as it's an agonist, not an antagonist, and would increase the activity of the α2 receptors, leading to decreased sympathetic tone and potentially decreased heart rate and blood pressure.

**Clinical Pearl / High-Yield Fact**
Selective α2 adrenergic receptor antagonists can be used to treat conditions such as orthostatic hypotension, where there is a significant drop in blood pressure upon standing. These drugs can help increase sympathetic tone and improve blood pressure regulation in these patients.

**Correct Answer: C. Yohimbine**