**Core Concept**
A spongy appearance with sunburst calcification is a characteristic radiological feature seen in certain types of osteogenic sarcoma, particularly the telangiectatic variant. This appearance is due to the presence of lytic lesions with internal calcifications that resemble a sunburst pattern.

**Why the Correct Answer is Right**
The telangiectatic osteosarcoma is characterized by the presence of large, cystic, lytic lesions within the bone, often with a sunburst pattern of calcification. This is due to the rapid growth of the tumor, which leads to the formation of a network of blood vessels and subsequent calcification within the lesion. The spongy appearance is a result of the lytic nature of the tumor, which causes the bone to appear porous and irregular.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe the characteristic radiological features of telangiectatic osteosarcoma. Other types of osteosarcoma may have different radiological appearances, but the spongy appearance with sunburst calcification is specific to telangiectatic osteosarcoma.
**Option B:** This option is incorrect because it describes a different type of bone lesion altogether. Osteoblastoma is a rare, benign bone tumor that typically presents as a well-defined, lytic lesion, but it does not have the characteristic sunburst calcification seen in telangiectatic osteosarcoma.

**Clinical Pearl / High-Yield Fact**
Telangiectatic osteosarcoma is a highly aggressive variant of osteosarcoma that often presents with a high level of metastatic disease at diagnosis. It is essential to recognize the characteristic radiological features of this tumor to ensure prompt diagnosis and treatment.

**Correct Answer: C. Telangiectatic osteosarcoma**