Scatter radiation at _ from the patient could be as high as 500 millirads per hour.

The correct choice indicates that scatter radiation from a patient can be measured at a distance of 5 feet, where levels could reach as high as 500 millirads per hour. This value underscores the significant impact that distance can have on radiation dose, highlighting the inverse square law principle, which states that the intensity of radiation diminishes with distance from the source.

At a distance of 5 feet, while the scatter radiation is still detectable, it is at a level that could be acknowledged in clinical practice, emphasizing the importance of maintaining adequate distance when working with fluoroscopy. This distance allows healthcare providers to manage exposure to scatter radiation effectively, ensuring that personnel are protected while delivering the necessary care to patients.

In contrast, closer distances, such as 1 foot or 2 feet, would generally exhibit higher levels of scatter radiation, making it critical to adopt appropriate radiation protection measures, such as shielding and maintaining distance, to further reduce exposure risk. Understanding these principles is essential for both patient safety and the safety of healthcare workers in radiological environments.