**Core Concept**
The question is testing the identification of a specific lysosomal storage disorder based on the presence of histiocytes with PAS-positive Diastase-resistant material in the cytoplasm. This is a classic presentation of a disease where the accumulation of abnormal substances within the lysosomes of histiocytes leads to cellular dysfunction.

**Why the Correct Answer is Right**
The presence of PAS-positive Diastase-resistant material in the cytoplasm of histiocytes is indicative of the accumulation of glycogen-like material, which is a hallmark of Gaucher's disease. Electron-microscopic examination of these histiocytes is likely to reveal the presence of lipid-filled lysosomes, specifically Gaucher cells, which are characteristic of this disease. Gaucher cells contain large, membrane-bound vacuoles that are filled with glucocerebroside, a type of sphingolipid. This leads to the characteristic appearance of "crumpled tissue paper" or "wrinkled tissue paper" on electron microscopy.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is likely to be incorrect because it does not match the histological and ultrastructural findings described in the question.
* **Option B:** This option is likely to be incorrect because it does not match the specific characteristics of Gaucher cells or the accumulation of glucocerebroside in lysosomes.

**Clinical Pearl / High-Yield Fact**
Gaucher's disease is an autosomal recessive genetic disorder caused by a deficiency of the enzyme glucocerebrosidase, leading to the accumulation of glucocerebroside in lysosomes. It is the most common lysosomal storage disorder and can present with a wide range of symptoms, including hepatosplenomegaly, anemia, and delayed milestones.

**Correct Answer:** C.