Final answer:
Osteoporosis requires a decreased radiographic exposure technique because it is characterized by decreased bone density, leading to weakened bones. Therefore, the correct option is a.
Step-by-step explanation:
The pathological condition that would require a decrease in exposure technique is osteoporosis. Osteoporosis involves a decrease in bone mass and density, leading to weakened bones that are more prone to fracture. Because osteoporotic bones are less dense, they require less radiation to achieve the same imaging quality as normal bones, thus requiring decreased exposure during radiographic imaging. On the other hand, conditions like pneumonia, osteopetrosis, and osteoarthritis may require increased exposure due to factors such as fluid in the lungs, increased bone density, or changes in joint space respectively.