**Core Concept**
Gaucher's disease is a genetic disorder characterized by the accumulation of glucocerebroside, a type of sphingolipid, in various organs due to a deficiency of an enzyme responsible for its breakdown. This deficiency leads to the accumulation of glucocerebroside, causing cellular damage and organ dysfunction.

**Why the Correct Answer is Right**
The enzyme responsible for breaking down glucocerebroside is glucocerebrosidase. This enzyme catalyzes the conversion of glucocerebroside to glucose and ceramide. In Gaucher's disease, mutations in the GBA gene lead to a deficiency of glucocerebrosidase, resulting in the accumulation of glucocerebroside. This accumulation causes the characteristic clinical features of the disease, including anemia, thrombocytopenia, and hepatosplenomegaly.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to Gaucher's disease. Glucose-6-phosphatase is an enzyme involved in glucose metabolism, and its deficiency is associated with a different genetic disorder, glycogen storage disease type Ia.
* **Option B:** This option is incorrect because sphingomyelinase is the enzyme deficient in Niemann-Pick disease, not Gaucher's disease.
* **Option D:** This option is not relevant to Gaucher's disease. Arylsulfatase A is an enzyme involved in the breakdown of sulfatides, and its deficiency is associated with a different genetic disorder, metachromatic leukodystrophy.

**Clinical Pearl / High-Yield Fact**
Gaucher's disease is an autosomal recessive disorder, meaning that individuals must inherit two copies of the mutated GBA gene (one from each parent) to develop the disease. This highlights the importance of genetic counseling for families with a history of Gaucher's disease.

**Correct Answer: C. Glucocerebrosidase**