**Core Concept**
Postmenopausal osteoporosis is a condition characterized by decreased bone density and increased risk of fractures, primarily due to estrogen deficiency. Non-hormonal drugs aim to prevent bone resorption or promote bone formation without affecting hormone levels.

**Why the Correct Answer is Right**
The correct answer is **Bisphosphonates**. Bisphosphonates, such as alendronate (Fosamax) and risedronate (Actonel), work by inhibiting osteoclast-mediated bone resorption. They bind to hydroxyapatite in bone, making it difficult for osteoclasts to break down bone tissue. This leads to an increase in bone density, thereby reducing the risk of fractures. Bisphosphonates are the most commonly used non-hormonal medications for preventing postmenopausal osteoporosis.

**Why Each Wrong Option is Incorrect**
* **Option A:** Raloxifene (Evista) is a selective estrogen receptor modulator (SERM), which means it has estrogen-like effects on some tissues, making it a hormonal drug.
* **Option C:** Calcitonin is a hormone that helps regulate calcium levels in the blood, making it a hormonal drug.
* **Option D:** Denosumab (Prolia) is a monoclonal antibody that targets RANKL, a protein involved in bone resorption. While it is a non-hormonal drug, it is not a bisphosphonate.

**Clinical Pearl / High-Yield Fact**
Bisphosphonates are effective in preventing osteoporotic fractures but have a risk of atypical femoral fractures (AFFs), especially with long-term use. Patients on bisphosphonates should be monitored for signs of AFFs, such as thigh pain or deformity.

**Correct Answer:** B. Bisphosphonates