**Core Concept:** Retinoblastoma is a rare tumor of the retina, primarily affecting children, which develops from the retinal stem cells. It is classified as either intraocular or extraocular, with intraocular retinoblastoma being the focus of this question. The correct statement should address the nature of intraocular retinoblastoma.

**Why the Correct Answer is Right:** The correct answer, **C. Intraocular retinoblastoma is an embryonal tumor**, refers to the fact that retinoblastoma develops from the embryonic cells of the retina. This is true, as retinoblastoma is primarily caused by mutations in the RB1 tumor suppressor gene, which is active during embryonic development.

**Why Each Wrong Option is Incorrect:**

A. **Intraocular retinoblastoma is a malignant tumor:** While retinoblastoma is a malignant tumor, the correct statement should differentiate between intraocular and extraocular retinoblastoma.

B. **Intraocular retinoblastoma is a benign tumor:** Retinoblastoma is a malignant tumor, not a benign one. This option is incorrect as it contradicts the true nature of the disease.

D. **Intraocular retinoblastoma develops in adults only:** Retinoblastoma primarily affects infants and children, not adults. This option is incorrect as it fails to address the age group most commonly affected by the disease.

**Clinical Pearl / High-Yield Fact:** Understanding the correct classification of retinoblastoma as an intraocular malignant tumor affecting infants and children is crucial for appropriate diagnosis and treatment planning. This knowledge helps in distinguishing it from other ocular tumors and guiding decisions regarding enucleation, chemotherapy, or focal treatment modalities.