**Core Concept**
Wilson's disease is a rare genetic disorder characterized by excessive accumulation of copper in the body, particularly in the liver, brain, and other organs. This accumulation leads to cellular damage and dysfunction. The disease is caused by mutations in the ATP7B gene, which plays a crucial role in regulating copper transport and metabolism.

**Why the Correct Answer is Right**
The correct answer, **Increased urinary copper excretion**, is a hallmark of Wilson's disease. In this condition, the liver accumulates copper, which is then released into the bloodstream and excreted in the urine. The increased urinary copper excretion is a result of the body's attempt to eliminate the excess copper. This is often measured through a 24-hour urine collection test, which can help diagnose Wilson's disease. The mutation in the ATP7B gene leads to impaired copper transport, causing the liver to accumulate copper and the kidneys to excrete more copper in the urine.

**Why Each Wrong Option is Incorrect**
**Option A:** Increased serum ceruloplasmin is actually a characteristic of Wilson's disease, but it's not the correct answer. Serum ceruloplasmin levels are typically low in Wilson's disease, as the mutation in the ATP7B gene impairs the incorporation of copper into ceruloplasmin. However, the question is asking for a true statement about Wilson's disease, and increased urinary copper excretion is a more specific and accurate indicator of the disease.

**Option B:** Decreased liver copper is incorrect, as Wilson's disease is characterized by increased liver copper accumulation. The mutation in the ATP7B gene impairs copper transport out of the liver, leading to accumulation of copper in this organ.

**Option D:** Decreased urine copper excretion is also incorrect, as Wilson's disease is associated with increased urinary copper excretion. The body attempts to eliminate excess copper through the kidneys, leading to increased copper excretion in the urine.

**Clinical Pearl / High-Yield Fact**
Wilson's disease is a classic example of a "leaky" gene, where a mutation in a single gene leads to a complex disorder with multiple systemic manifestations. The disease can present with a wide range of symptoms, including liver disease, neurological symptoms, and psychiatric manifestations.

**✓ Correct Answer: C. Increased urinary copper excretion**