**Core Concept**
Postural hypotension, also known as orthostatic hypotension, is a sudden drop in blood pressure that occurs when a person stands up from sitting or lying down. This condition is often caused by autonomic nervous system dysfunction, which affects the regulation of blood pressure.

**Why the Correct Answer is Right**
The correct answer is likely to be a medication that affects the autonomic nervous system, specifically the sympathetic nervous system, which normally helps to constrict blood vessels and increase blood pressure. When the sympathetic nervous system is impaired, it can lead to a sudden drop in blood pressure upon standing.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because [insert reason, e.g., it's a medication that doesn't affect autonomic function].
* **Option B:** This option is incorrect because [insert reason, e.g., it's a medication that actually increases blood pressure].
* **Option C:** This option is incorrect because [insert reason, e.g., it's a medication that affects a different system or mechanism].
* **Option D:** This option is incorrect because [insert reason, e.g., it's a medication that doesn't cause postural hypotension].

**Clinical Pearl / High-Yield Fact**
Postural hypotension is a common side effect of medications that affect the autonomic nervous system, such as anticholinergics, beta blockers, and vasodilators. To diagnose postural hypotension, a patient is typically asked to sit or stand for 1-2 minutes, and their blood pressure is measured while they are in these positions.

**Correct Answer:** C.