**Core Concept**
SLE (Systemic Lupus Erythematosus) is a chronic autoimmune disease that can affect multiple organ systems, including the kidneys. The characteristic kidney lesion in SLE is a result of immune complex deposition, which triggers an inflammatory response and subsequent tissue damage.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of SLE nephritis, where immune complexes consisting of antigen-antibody complexes deposit in the glomeruli. This leads to activation of the complement system, particularly the C3 convertase, which results in the formation of subendothelial immune deposits. The subsequent inflammatory response causes proliferation of mesangial cells and endothelial cells, resulting in the characteristic "full-house" lesion.

**Why Each Wrong Option is Incorrect**
* **Option A:** Mesangial proliferative glomerulonephritis is more characteristic of IgA nephropathy, not SLE.
* **Option B:** Focal segmental glomerulosclerosis (FSGS) is a primary cause of nephrotic syndrome and is not directly related to SLE.
* **Option C:** Membranous nephropathy is characterized by thickening of the glomerular basement membrane due to immune complex deposition, but it is not the characteristic lesion in SLE.

**Clinical Pearl / High-Yield Fact**
The "full-house" lesion in SLE nephritis consists of 5 components: mesangial proliferation, endocapillary proliferation, subendothelial immune deposits, subepithelial immune deposits, and crescent formation.

**Correct Answer:** C.