You're volunteering with the National Oceanic and Atmospheric Administration (NOAA) as a diver. Read the following excerpt from an NOAA policy for divers, and then use context clues to answer the question. Reserve Air Supply System (RASS) is a diver-carried auxiliary supply of air, nitrox, or mixed gas that's sufficient to allow the diver to reach the surface, or another source of breathing gas, or to be reached by a standby diver. A RASS must be worn for all NOAA "scientific" SCUBA dives conducted: outside the no-decompression limits; in overhead environments where direct ascent to the surface is prevented by an obstruction; in conditions of low visibility where the diver cannot read the cylinder pressure gauge; in enclosed or physically confined spaces; deeper than 100 feet; by solo divers being line tended; and when deemed appropriate by the diver in charge of the dive. As used in the document, what is meant by "Reserve Air Supply System"? equipment that divers wear to help them ascend to the surface or another air supply equipment that divers under training need to wear during dives equipment that helps divers breathe underwater after they run out of oxygen equipment that improves divers' visibility in