**Core Concept**
Good-pasture syndrome is a rare autoimmune disorder characterized by the presence of anti-neutrophil cytoplasmic antibodies (ANCA) that target the basement membranes of the lungs and kidneys. This condition leads to rapidly progressive glomerulonephritis and pulmonary hemorrhage.

**Why the Correct Answer is Right**
The organ primarily involved in Good-pasture syndrome is the kidney. The ANCA antibodies target the type IV collagen in the glomerular basement membrane, leading to damage and destruction of the glomeruli. This results in a loss of kidney function and the characteristic renal manifestations of the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** The lungs are also involved in Good-pasture syndrome, but they are not the primary organ affected.
**Option B:** The liver is not directly involved in the pathophysiology of Good-pasture syndrome.
**Option C:** The heart is not a primary target of the ANCA antibodies in Good-pasture syndrome.

**Clinical Pearl / High-Yield Fact**
Good-pasture syndrome is often associated with the presence of ANCA, particularly anti-GBM antibodies, which can be detected in the serum of affected patients. This is a crucial diagnostic clue that can help differentiate it from other autoimmune disorders.

**Correct Answer:** C.