When Doors to Radiographic and Fluoroscopic Rooms Are Closed During

When doors to radiographic and fluoroscopic rooms are closed during radiation exposures,a substantial degree of protection is provided for persons in areas adjacent to the room door.This is because in most facilities room doors have attenuation for diagnostic energy x-ray equivalent to that provided by _______ mm of lead.

A) 0.2
B) 0.4
C) 0.6
D) 0.8