**Core Concept**
The question is testing knowledge of intra-abdominal tumors in children, specifically the most common tumor type in the 2-5 years age group. This requires understanding of pediatric abdominal pathology and tumor epidemiology.

**Why the Correct Answer is Right**
The commonest intra-abdominal tumor in children between 2-5 years is a neuroblastoma. This tumor arises from the neural crest cells of the sympathetic nervous system and is often located in the adrenal glands. Neuroblastomas are known for their rapid growth and potential for metastasis. The high incidence in this age group is attributed to the development of these cells during fetal life and early childhood.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the topic of intra-abdominal tumors in children.
* **Option B:** Wilms tumor is a common renal tumor in children, but it is not the most common intra-abdominal tumor in the 2-5 years age group.
* **Option C:** Hepatoblastoma is a rare malignant liver tumor in children, but it is not as common as neuroblastoma in the 2-5 years age group.

**Clinical Pearl / High-Yield Fact**
Neuroblastoma is the most common extracranial solid tumor in children, and its diagnosis often requires a combination of imaging studies, tumor markers, and histopathological examination.

**Correct Answer: C. Hepatoblastoma.**