Final answer:
A typical tank in an open-circuit scuba system provides enough air for a moderate, short dive to moderate depths. Deeper or longer dives require different gas mixtures or equipment due to increased underwater pressure and risks such as decompression sickness.
Step-by-step explanation:
One tank in an open-circuit scuba system typically supplies enough air for a moderate, short dive to moderate depths. These scuba tanks contain compressed air, which expands to fill the shape and volume of its container and can also be compressed so that a large amount of gas can be forced into a small container. When considering the compressibility of gases, a typical scuba tank at 200 to 300 atmospheres pressure, if decompressed to 1 atmosphere, would fill a volume of about 2500 liters.
For deeper or longer dives, special equipment or gas mixtures may be required due to the increased pressure at depth and the potential for nitrogen narcosis and decompression sickness (DCS). Recreational scuba divers using common compressed air tanks frequently adhere to the no-decompression limits, which restrict the depth and duration of dives to prevent the need for decompression stops. In contrast, deep-sea divers might need special gas mixtures, such as a combination of helium and oxygen, to handle high-pressure environments and to avoid DCS during ascent.
Therefore, the correct answer to the question regarding the air supply of one tank in an open-circuit scuba system is option C) Moderate, short dive.