Final answer:
The correct answer is B. Slit camera. A slit camera is a device used to evaluate focal spot accuracy in radiography.
Step-by-step explanation:
The correct answer is B. Slit camera. A slit camera is a device used to evaluate focal spot accuracy in radiography. It requires two exposures to evaluate focal spot accuracy because it uses a narrow slit to produce a thin line of radiation, which is then imaged onto an image receptor. By evaluating the sharpness and width of the line produced by the slit, the accuracy of the focal spot can be determined.