Final answer:
The best combination for scatter clean-up would be a larger target angle with a smaller actual focal spot. Therefore, option (C) with a 17-degree target angle and a 0.6-mm actual focal spot would be the most effective for grid efficiency.
Step-by-step explanation:
The question pertains to scatter clean-up or grid efficiency in the context of X-ray imaging. By comparing the effectiveness of scatter clean-up between different target angles and focal spot sizes, we can determine which combination delivers better grid efficiency. When it comes to grid efficiency, a smaller actual focal spot size typically results in better detail because it produces a more defined, less blurry image. Thus, among the options given, a smaller actual focal spot size and a larger target angle are more desirable for scatter clean-up. Therefore, combination (C) 17-degree target angle, with a 0.6-mm actual focal spot, would be the best option for producing the best scatter clean-up. The larger target angle aids in the reduction of scatter by increasing the angle of incidence, which helps in achieving better grid efficiency.