**Core Concept**
Minimal-change nephropathy is a type of nephrotic syndrome characterized by the loss of large amounts of protein in the urine, resulting from damage to the glomeruli. It is the most common cause of nephrotic syndrome in children. The **pathophysiology** involves podocyte injury, leading to altered glomerular permeability.

**Why the Correct Answer is Right**
The correct answer is related to the characteristic features of minimal-change nephropathy. This condition is known for being the commonest cause of the nephrotic syndrome in childhood, making option a correct. It often responds well to steroid therapy, but relapses can occur. The proteinuria in minimal-change disease is typically highly selective, meaning that mostly albumin is lost in the urine.

**Why Each Wrong Option is Incorrect**
**Option B:** This is incorrect because minimal-change nephropathy can relapse after remission. **Option C:** While it's true that minimal-change disease produces highly selective proteinuria, this option is not the best answer choice based on the question's requirements. **Option D:** This is incorrect because serum complement levels are typically normal in minimal-change disease. **Option E:** This is incorrect because while renal biopsy can confirm the diagnosis, it is not always necessary, especially in children with a classic presentation.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that minimal-change nephropathy is highly responsive to corticosteroid therapy, which is a crucial aspect of its management. This condition's characteristic selective proteinuria and normal serum complement levels are also important for diagnosis.

**Correct Answer:** A. Is the commonest cause of the nephrotic syndrome in childhood