**Core Concept**
Acute hypercalcemia is a medical emergency requiring prompt treatment to alleviate symptoms and prevent complications. The goal of therapy is to decrease calcium levels, either by increasing renal excretion or reducing bone resorption. Various pharmacological agents and non-pharmacological interventions are employed to manage this condition.

**Why the Correct Answer is Right**
Gallium Nitrate is not typically used to treat acute hypercalcemia. It is a bisphosphonate analogue that inhibits bone resorption and is primarily used for the treatment of tumor-induced hypercalcemia and Paget's disease. However, its onset of action is too slow to be effective in the acute setting. In contrast, other options like hydration with saline, calcitonin, and bisphosphonates can be used to rapidly decrease calcium levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Hydration with saline is a crucial initial step in managing acute hypercalcemia, as it helps to increase renal calcium excretion and reduce calcium levels.
**Option B:** Calcitonin is a hormone that inhibits osteoclast activity, reducing bone resorption and lowering calcium levels. It is often used in the initial management of acute hypercalcemia.
**Option C:** Bisphosphonates, such as pamidronate or zoledronic acid, are potent inhibitors of bone resorption and are commonly used to treat acute hypercalcemia, particularly in patients with malignancy.

**Clinical Pearl / High-Yield Fact**
In the management of acute hypercalcemia, it's essential to remember that hydration with saline is the first line of treatment, and bisphosphonates are often used in conjunction with other agents to rapidly decrease calcium levels.

**✓ Correct Answer: D. Gallium Nitrate**