**Core Concept**
Multiple myeloma is a plasma cell disorder characterized by excessive production of monoclonal immunoglobulins, leading to hypercalcemia due to increased osteoclast activity, bone destruction, and parathyroid hormone-related protein (PTHrP) secretion. Hypercalcemia in multiple myeloma typically presents with symptoms such as nausea, vomiting, and altered mental status.

**Why the Correct Answer is Right**
Option A, Oral pamidronate, is correct because bisphosphonates like pamidronate inhibit osteoclast-mediated bone resorption, reducing hypercalcemia in multiple myeloma patients. Option C, Mithramycin, is also correct as it is a calcimimetic agent that inhibits PTHrP secretion and reduces bone resorption. Option D, Glucocorticoids, is correct because they can reduce bone resorption and have anti-tumor effects in multiple myeloma.

**Why Each Wrong Option is Incorrect**
**Option B:** Less than 15mg/dl serum calcium does not cause symptoms is incorrect because even mild hypercalcemia can cause symptoms such as nausea and vomiting.

**Option E:** is not present in the options.

**Clinical Pearl / High-Yield Fact**
It is essential to note that patients with multiple myeloma and hypercalcemia often require immediate hydration and treatment with bisphosphonates or glucocorticoids to rapidly lower serum calcium levels.

**Correct Answer:**
✓ Correct Answer: B. acd