**Core Concept**
The patient's presentation with generalized edema, hypertension, subnephrotic proteinuria, microscopic hematuria, decreased serum complement levels, and positive anti-hepatitis C antibodies suggests an immune-mediated glomerulonephritis associated with hepatitis C virus (HCV) infection.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with membranoproliferative glomerulonephritis (MPGN), a type of glomerulonephritis characterized by the deposition of immune complexes in the glomeruli. HCV infection is a known cause of MPGN, leading to the activation of the complement system and the subsequent deposition of immune complexes in the glomeruli. The decreased serum complement levels and the presence of anti-HCV antibodies support this diagnosis.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while IgA nephropathy can present with hematuria and proteinuria, the presence of anti-HCV antibodies and decreased serum complement levels is not typical of this condition.
* **Option B:** This option is incorrect because while lupus nephritis can present with a similar clinical picture, the presence of anti-HCV antibodies is not a characteristic feature of this condition.
* **Option C:** This option is incorrect because while diabetic nephropathy can present with proteinuria and hypertension, the presence of anti-HCV antibodies and decreased serum complement levels is not typical of this condition.

**Clinical Pearl / High-Yield Fact**
The presence of anti-HCV antibodies in a patient with glomerulonephritis should prompt a search for HCV infection, which can be detected by serological tests or molecular assays. Early identification and treatment of HCV infection can help prevent the progression of kidney disease.

**Correct Answer:** C. Membranoproliferative glomerulonephritis associated with hepatitis C virus infection.