**Core Concept**
The question is testing the effect of various antihypertensive drugs on plasma renin activity. Plasma renin is an enzyme that plays a crucial role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure. The RAAS pathway involves the conversion of angiotensinogen to angiotensin I, followed by the conversion to angiotensin II, a potent vasoconstrictor.

**Why the Correct Answer is Right**
The correct answer is a drug that does not increase plasma renin activity. Drugs that increase plasma renin activity typically act on the renin-angiotensin-aldosterone system to increase blood pressure. For instance, ACE inhibitors (such as captopril) and angiotensin II receptor blockers (such as losartan) increase plasma renin activity as a compensatory mechanism to counteract the decreased angiotensin II levels.

**Why Each Wrong Option is Incorrect**
* **Option A:** This drug increases plasma renin activity by blocking the conversion of angiotensin I to angiotensin II, leading to increased production of angiotensin II through the renin-angiotensin-aldosterone system.
* **Option B:** This drug increases plasma renin activity by blocking the action of angiotensin II on its receptors, leading to increased production of angiotensin II through the renin-angiotensin-aldosterone system.
* **Option D:** This drug increases plasma renin activity by blocking the conversion of angiotensin I to angiotensin II, leading to increased production of angiotensin II through the renin-angiotensin-aldosterone system.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that ACE inhibitors and angiotensin II receptor blockers increase plasma renin activity as a compensatory mechanism. This can lead to hyperkalemia, especially in patients with renal impairment.

**Correct Answer: A. Captopril**