**Core Concept**
Bone forming tumors are a type of primary bone malignancy characterized by excessive bone matrix deposition. These tumors often arise from osteoblasts, the cells responsible for bone formation.

**Why the Correct Answer is Right**
Osteoid osteoma and osteoblastoma are indeed bone-forming tumors. Osteoid osteoma is a small, benign tumor that typically causes night pain due to the release of prostaglandins. It is characterized by the presence of osteoid matrix and a central nidus, surrounded by a zone of reactive bone formation. Osteoblastoma is a rare, benign tumor that also exhibits features of bone formation, including the presence of osteoid matrix and an increased number of osteoblasts. Both of these tumors arise from osteoblasts and exhibit excessive bone matrix deposition.

**Why Each Wrong Option is Incorrect**
**Option A:** Osteosarcoma is a malignant bone tumor that exhibits features of both osteoblastic and osteoclastic activity, but it is not typically classified as a bone-forming tumor. Instead, it is characterized by the presence of malignant osteoblasts and osteoclasts.

**Option C:** Giant cell tumor is a type of benign bone tumor characterized by the presence of giant cells and osteoclasts. While it can exhibit some features of bone formation, it is not typically classified as a bone-forming tumor.

**Option D:** Chondrosarcoma is a malignant bone tumor that exhibits features of cartilage formation, rather than bone formation.

**Option E:** This option is blank and should be ignored.

**Clinical Pearl / High-Yield Fact**
Remember that bone-forming tumors are often characterized by excessive bone matrix deposition and the presence of osteoid matrix. This can help distinguish them from other types of bone tumors, such as osteoclastic or cartilaginous tumors.

**Correct Answer:** B. Osteoid osteoma.