**Core Concept**
Multiple Myeloma is a plasma cell malignancy characterized by the proliferation of malignant plasma cells in the bone marrow, leading to various clinical and laboratory abnormalities. The diagnosis of Multiple Myeloma is typically based on both major and minor criteria, which include specific clinical, laboratory, and radiological features.

**Why the Correct Answer is Right**
The minor criteria of Multiple Myeloma include anemia (Hb 12 mg/dL), renal insufficiency (Cr > 2 mg/dL), and bone marrow plasmacytosis (plasma cells > 30% of bone marrow cells). These criteria are used in conjunction with major criteria (such as biopsy-proven plasma cell myeloma) to establish a diagnosis of Multiple Myeloma.

**Why Each Wrong Option is Incorrect**
* **Option A:** Anemia is indeed a minor criterion of Multiple Myeloma, as it is a common feature of the disease due to bone marrow infiltration by malignant plasma cells.
* **Option B:** Bone lesions are also a minor criterion of Multiple Myeloma, as they are a hallmark of the disease and result from the proliferation of malignant plasma cells in the bone marrow.
* **Option D:** Bone marrow plasmacytosis is another minor criterion of Multiple Myeloma, as it reflects the infiltration of the bone marrow by malignant plasma cells.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the diagnosis of Multiple Myeloma requires both major and minor criteria to be met, as the presence of one or more minor criteria alone is not sufficient for a diagnosis.

**Correct Answer:** C.