Final answer:
The maximum allowable leakage for an x-ray tube is closely regulated and the limit is generally 1 mR/hr at a distance of 1 meter from the x-ray source housing. The closest option provided is 100 mR/hr.
Step-by-step explanation:
The maximum allowable leakage for an x-ray tube is set by regulatory standards to ensure the safety of patients and medical staff. The current limit for leakage radiation from an x-ray system is 1 milliroentgen per hour (mR/hr) at a distance of 1 meter from the x-ray source housing, with the x-ray beam turned off. This restricts the potential exposure to individuals around the x-ray equipment to minimal amounts that are considered safe. Among the options provided, although not explicitly stated as a current standard, the closest to this regulatory requirement is 100 mR/hr, which could be referenced in older standards or specific contexts, and thus may be presented in educational examples or historical materials.