The correct answer is B.
The allowable public exposure limit is 100 millirem per year in addition to normal background radiation.
Section 2, Part 1, (213) in the DOE Radiological Control Handbook gives, in table 2-1, 0.1 rem as the limit for whole body radiation to visitors and the public, and 5 rem whole body radiation as the limit for
radiological workers. Note 3 to this table states, "Exposure due to background radiation, ...medical procedures, and voluntary participation in medical research programs shall not be included in either personnel
radiation dose records, or assessment of dose against the limits of this table". In addition, it is stated that exposures shall be well below these limits, and as low as reasonably possible. Other limits are
established for extremities, individual organs, and pregnant workers.