**Core Concept**
The question requires knowledge of the pharmacological management of diabetic nephropathy, specifically the use of ACE inhibitors to retard the progression of renal disease. Diabetic nephropathy is a common complication of type 2 diabetes mellitus, characterized by albuminuria and progressive renal fibrosis.

**Why the Correct Answer is Right**
Enalapril, an angiotensin-converting enzyme (ACE) inhibitor, is a first-line treatment for diabetic nephropathy. ACE inhibitors work by blocking the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor that also stimulates aldosterone secretion. By reducing angiotensin II levels, ACE inhibitors decrease intraglomerular pressure, which slows the progression of renal disease. Enalapril also has a mild diuretic effect and reduces proteinuria.

**Why Each Wrong Option is Incorrect**
**Option A:** Hydrochlorothiazide is a thiazide diuretic that can worsen albuminuria and increase the risk of renal disease progression. Thiazide diuretics can cause volume depletion, which can further increase intraglomerular pressure.

**Option C:** Amiloride is a potassium-sparing diuretic that can be used in combination with ACE inhibitors to manage hypertension and proteinuria. However, as a monotherapy, it is not as effective as ACE inhibitors in retarding the progression of renal disease.

**Option D:** Aspirin is an antiplatelet agent used primarily to prevent cardiovascular events. It does not have a direct effect on the progression of renal disease and may even increase the risk of bleeding in patients with renal impairment.

**Clinical Pearl / High-Yield Fact**
It is essential to note that ACE inhibitors should be used in conjunction with other antihypertensive agents to achieve optimal blood pressure control. Additionally, patients with diabetic nephropathy should be closely monitored for signs of renal impairment, such as worsening proteinuria or decreased glomerular filtration rate.

**✓ Correct Answer:** B. Enalapril