**Core Concept**
Subsurface porosity refers to the presence of pores or voids in the bone structure, particularly in the cortical layer. This porosity is crucial in the regulation of bone strength, density, and mineralization. Decreasing subsurface porosity can affect bone quality and increase the risk of osteoporosis.

**Why the Correct Answer is Right**
Decreasing subsurface porosity can be achieved through the administration of bisphosphonates. These medications work by inhibiting osteoclast-mediated bone resorption, leading to an increase in bone density and a reduction in porosity. Bisphosphonates bind to hydroxyapatite in bone, making it difficult for osteoclasts to resorb bone tissue. This results in a decrease in bone turnover and, subsequently, a decrease in subsurface porosity.

**Why Each Wrong Option is Incorrect**
**Option A:** While certain medications may affect bone density, this option is not the most accurate choice for decreasing subsurface porosity.
**Option B:** This option may not be directly related to decreasing subsurface porosity and could be a distractor for students who are not familiar with the specific effects of various medications on bone health.
**Option C:** This option may be related to other aspects of bone health but is not the most accurate choice for decreasing subsurface porosity.

**Clinical Pearl / High-Yield Fact**
Bisphosphonates are commonly used in the treatment of osteoporosis and Paget's disease. They work by inhibiting bone resorption, which leads to an increase in bone density and a decrease in subsurface porosity.

**Correct Answer:** A. Bisphosphonates.