**Core Concept**
The Finnish type of Congenital Nephrotic syndrome is a rare genetic disorder characterized by massive proteinuria and nephrotic syndrome in infants. It is caused by a mutation in a specific gene that encodes a crucial protein in the kidney's filtration apparatus.

**Why the Correct Answer is Right**
The Finnish type of Congenital Nephrotic syndrome is caused by a mutation in the NPHS1 gene, which encodes for the protein Nephrin. Nephrin is a key component of the slit diaphragm, a critical structure in the glomerular filtration barrier that prevents large molecules from passing through the kidneys. The mutation leads to a disruption in the slit diaphragm, resulting in massive proteinuria and nephrotic syndrome. The NPHS1 gene is specifically mutated in the Finnish type of Congenital Nephrotic syndrome, which explains the high incidence of this disorder in Finland.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the Finnish type of Congenital Nephrotic syndrome. While mutations in other genes can cause similar disorders, the NPHS1 gene is specifically implicated in this condition.
* **Option B:** This option is incorrect because the Finnish type of Congenital Nephrotic syndrome is caused by a mutation in the NPHS1 gene, not the NPHS2 gene.

**Clinical Pearl / High-Yield Fact**
The Finnish type of Congenital Nephrotic syndrome is an autosomal recessive disorder, meaning that affected individuals inherit two copies of the mutated gene, one from each parent. This highlights the importance of genetic counseling for families with a history of this disorder.

**Correct Answer:** C. Nephrin.